C. Domingo

Vibrational study of the interaction of dinaphthalenic Ni(II) and Cu(II) azamacrocycle complexes methyl and phenyl substituted with different metal surfaces

Abstract The FT-IR and Raman spectra in the solid state, the reflection–absorption IR spectra (RAIRS) and the surface enhanced IR (SEIR) and surface enhanced Raman spectra (SERS) of the Ni(II) (trans-7,14-dimethyl-5,12,-diphenyl-1,4,8,11-tetra-aza-2,3-9,10-dinaphthyl-cyclotetradeca-5,7,12,14-tetraene) and Cu(II) (5,7,12,14-tetramethyl-1,4,8,11-tetra-aza-2,3-9,10-dinaphthyl-cyclotetradeca-5,7,12,14-tetraene) are reported. The RAIRS analysis and differences observed in the relative intensities of complexes deposited onto KBr and Cu surfaces suggest that the organisation of each macrocycle is different on both surfaces. SERS data allow to propose for both complexes an adsorbate–substrate interaction between the complex and the colloidal Ag surface. Complexes are oriented face-on to the surface being the number of Cu macrocycles oriented face-on to the surface larger than that of the Ni macrocycles. The organisation of the complexes on Au film is different to that found on Ag colloids and rather random. The phenyl groups avoid a better organisation of the Ni complex on the surface. SEIR data analysis of samples deposited on Au film suggests that the Ni complex is less organised than the Cu complex. The dynamic and energetic of the adsorbate–substrate interaction is interpreted by using a simple molecular model and INDO/1 calculations.

Effect of Metal–Liquid Interface Composition on the Adsorption of a Cyanine Dye onto Gold Nanoparticles

Synthesis of asymmetric nanoparticles, such as gold nanorods, with tunable optical properties providing metal structures with improved SERS performance is playing a critical role in expanding the use of SERS to imaging and sensing applications. However, the synthetic methods usually require surfactants or polymers as shape-directing agents. These chemicals normally remain firmly bound to the metal after the synthesis, preventing the direct adsorption of a large number of potential analytes and often hampering the chemical functionalization of the surface unless extended, and critical for the nanoparticle stability, postremoval steps were performed. For this reason, it is of great importance for the full exploitation of these nanostructures to gain a deeper insight into the dependence of the analyte-metal interaction to the metal-liquid interface composition. In this article, we investigated in detail the role played by each component of the gold nanorod (GNR) interface in the adsorption of indocyanine green (ICG) as a probe molecule. Citrate-reduced gold nanospheres were used as a model substrate since the negative citrate anions adsorbed onto the metal surface can be easily displaced by those chemicals usually involved in the GNR synthesis, allowing the GNR-like interface composition to be progressively rebuilt and modified at will on the citrate-capped nanoparticles. The obtained results provide a meticulous description of the role played by each individual component of the metal-liquid interface on the ICG interaction with the metal, illustrating how apparently minor experimental changes can dramatically modify the affinity and optical properties of the ICG probe adsorbed onto the nanoparticle.

Diagnostics and modeling of glow discharges by time-resolved IR absorption spectroscopy

In this work, several applications of time resolved absorption spectroscopy, with different time scales and spectral resolutions, are described for the diagnostic and modeling of cold plasmas produced in square wave modulated hollow cathode discharges. These methods have revealed a very sensitive and efficient way to test the relevance of the different individual mechanisms, in comparison with the usual plasma diagnostic methods of the stationary state.

Gas phase FT-IR absorption spectroscopy as a quantitative diagnostic method for cold plasmas: Application to hollow cathode discharges of acetylene and sulfur reduced compounds (DMS and DMDS)

Abstract Gas phase compounds produced in low pressure dc hollow cathode flowing discharges of acetylene, dimethylsulfide (DMS) and dimethyldisulfide (DMDS) have been, by the first time, identified and quantitatively measured through in situ FT-IR absorption spectroscopy. Experimental discharge parameters have been varied in the ranges where stable enough plasmas were produced. A high conversion of precursors to non-volatile compounds is observed. Only diacetylene has been detected in the infrared spectra of acetylene/inert gas discharges, with yields between 3 and 13%. Its appearance indicates that the C 2 H radical is the main intermediate species produced in such discharges. CS 2 , CH 4 and C 2 H 2 have been the most abundant products detected in the infrared spectra of DMS and DMDS plasmas, their maximal yields being in the range 5–20%. The concurrent production of CO, CO 2 and OCS, with yields one to two orders of magnitude lower, must be attributed to oxidation processes of the precursors due to air traces in the discharge cell. No final gaseous compounds, either oxygenated or not, suggesting the production of the CH 3 S radical as intermediate species were detected in these plasmas. The results presented clearly prove that hollow cathode discharges (HCD) produce cold plasmas where high temperature chemistry is conducted.

Time-resolved FTIR spectroscopy and kinetic modeling of a low frequency modulated N 2 O hollow cathode discharge

Nitrous oxide, N2O is usually the major constituent in the plasma-enhanced chemical vapor deposition (PECVD) of silicon dioxide, SiO2, which finds widespread applications in the electronic industry.