Dynamic in situ spectroscopic ellipsometry studies of the chemical reaction between ferrous ion and 2,2'-bipyridine (bpy) in a thin Nafion film are presented. A simple prototype system composed of a thin Nafion film on a glass substrate was used throughout the work. The reaction was detected by optically monitoring the formation of the strongly absorbing complex ion, Fe(bpy)3(2+) (epsilon 520 = 7.70 x 10(3) M(-1) cm(-1) in 0.1 M NaCl). The changes in film optical constants, n and k, and the thickness upon exposure of it to various solutions were monitored in a flow cell with the film on the backside of the substrate relative to the interrogation by light. A "step-by-step" approach was used to isolate the component parts of the system in which the film was consecutively exposed to solutions in the following order: supporting electrolyte, bpy, and, last, ferrous iron solution. The optical properties of the materials were quantitatively described before and during mass transport within the film by modeling using the appropriate multilayer optical models, i.e., the Cauchy equation for nonabsorbing media and the Urbach and Tauc-Lorentz (oscillator) functions for a film that absorbed. The experiments done allowed study of the diffusion in the film and the chemical reactions that are important in the sensing scheme for ferrous iron. Ligand (bpy) diffusion followed a two-stage diffusion mechanism described by a Berens-Hopfenberg model for incremental sorption (D25 = 7.04 x 10(-13) cm2 s(-1)). The stabilities of the appropriate systems, i.e., Nafion film with bpy, iron, and iron complex, were studied by exposing equilibrated films to circulating supporting electrolyte solutions. The measurements gave important insights into a set of film chemical reactions and, in turn, selective film dynamics. This work exemplifies the usefulness of spectroscopic ellipsometry in monitoring the kinetics of a chemical reaction in situ, as well as the changes in the film physical properties under dynamic conditions.

A spectroelectrochemical sensor consisting of an indium tin oxide (ITO) optically transparent electrode (OTE) coated with a thin film of partially sulfonated polystyrene-blockpoly(ethylene-ran-butylene)-block-polystyrene (SSEBS) was developed for [Tc(dmpe)(3)](+) (dmpe = 1,2-bis(dimethylphosphino)ethane). [Tc(dmpe)(3)](+) was preconcentrated by ion-exchange into the SSEBS film after a 20 min exposure to aqueous [Tc(dmpe)(3)](+) solution, resulting in a 14-fold increase in cathodic peak current compared to a bare OTE. Colorless [Tc(dmpe)(3)](+) was reversibly oxidized to colored [Tc(dmpe)(3)](2+) by cyclic voltammetry. Detection of [Tc(dmpe)(3)](2+) was accomplished through emission spectroscopy by electrochemically oxidizing the complex from nonemissive [Tc(dmpe)(3)](+) to emissive [Tc(dmpe)(3)](2+). The working principle of the sensor consisted of electrochemically cycling between nonemissive [Tc(dmpe)(3)](+) and emissive [Tc(dmpe)(3)](2+) and monitoring the modulated emission (λ(exc) = 532 nm; λ(em) = 660 nm). The sensor gave a linear response over the concentration range of 0.16-340.0 μM of [Tc(dmpe)(3)](2+/+) in aqueous phase with a detection limit of 24 nM.

Anodic stripping voltammetry (ASV) determination of Pb2+, Cd2+, and Zn2+ was done using metal catalyst free carbon nanotube (MCFCN) electrodes. Osteryoung square wave stripping voltammetry (OSWSV) was selected for detection. The MCFCNTs are synthesized via Carbo Thermal Carbide Conversion method which leads to residual transition metal free in the CNT structure. The new material shows very good results in detecting heavy metal ions, such as Pb2+, Cd2+, and Zn2+. The calculated limits of detection were 13 nM, 32 nM and 50 nM for Pb2+, Cd2+ and Zn2+, respectively with a deposition time of 150 s.

The spectroelectrochemical sensor uses thin, solid polyelectrolyte films as an essential element in its operation. In this work we explored the potential of partially sulfonated polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SSEBS) thin polymer films for chemical sensing. Spectroscopic ellipsometry was used to measure optical and surface properties of the air-dried and hydrated material. SSEBS incorporates a relatively small amount of water (overall change of 25%) mainly determined by the complex dynamics of the film. The decrease in the refractive index after complete hydration of the film can be predicted based on the magnitude of swelling using effective medium approximation models. Adhesion of the material on various surfaces (glass, indium tin oxide, gold) was evaluated with the tape peel-off method. The ability of the SSEBS material to preconcentrate cations was evaluated by cyclic voltammetry, absorbance, and luminescence measurements using model analytes (Ru(bpy)(3)(2+), phenosafranine, and rhodamine 6G). The detection limits of the sensor for Ru(bpy)(3)(2+) under unoptimized conditions can be significantly improved if luminescence is used as the detection modality (DL = 5 x 10(-10) M) instead of absorbance (DL = 5 x 10(-7) M). Overall, the results demonstrate the effectiveness of the SSEBS material for spectroelectrochemical sensing.

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Four novel gold(III) complexes of general formulae [AuCl{(S,S)-Reddl}]PF (Reddl=O,O'-dialkyl-(S,S)-ethylenediamine-N,N'-di-2-(4-methyl)pentanoate, R=n-Pr, n-Bu, n-Pe, i-Bu; 1-4, respectively), were synthesized and characterized by elemental analysis, UV/Vis, IR, and NMR spectroscopy, as well as high resolution mass spectrometry. Density functional theory calculations pointed out that (R,R)-N,N'-configuration diastereoisomers were energetically the most favorable. Duo to high cytotoxic activity complex 3 was chosen for stability study in DMSO, no decomposition occurs within 24h, and for the reaction with ascorbic acid in which was reduced immediately. Additionally, 3 interacts with bovine serum albumin (BSA) as proven by UV/Vis spectroscopy. In vitro antitumor activity was determined against human cervix adenocarcinoma (HeLa), human myelogenous leukemia (K562), and human melanoma (Fem-x) cancer cell lines, as well as against non-cancerous human embryonic lung fibroblast cells MRC-5. The highest activity was observed against K562 cells (IC: 5.04-6.51μM). Selectivity indices showed that these complexes are less toxic than cisplatin. 3 had a similar viability kinetics on HeLa cells as cisplatin. Drug accumulation studies in HeLa cells showed that the total gold uptake increased much faster than that of cisplatin pointing out that 3 more efficiently enters the cells than cisplatin. Furthermore, morphological and cell cycle analysis reveal that gold(III) complexes induced apoptosis in time- and dose-dependent manner.

Dynamic in situ spectroscopic ellipsometry studies of poly(vinyl alcohol)−poly(acrylic acid) (PVA−PAA) composite films are presented. Thin films immobilized on glass substrates were conditioned over time in aqueous media. Dynamic measurements consisted of thickness (swelling ratio) and optical constant changes in time. The films displayed anomalous diffusion that was characterized by fast initial swelling followed by a much slower thickness reduction. A simple mechanism based on polymer network relaxation was proposed as the likely explanation for thickness reduction. A diffusion/relaxation formalism was used to quantitatively model measured data. From this modeling the diffusion coefficient of water and the network relaxation rate constants were estimated for three different types of composite films that differed in the degree of cross-linking. The diffusion Deborah number was estimated to be a high value ((DEB)D ≈ 5 × 103) which suggested elastic diffusion and non-Fickian behavior. Slow polymer network relaxation was the likely cause of a considerable amount of water expelled from the films. Alternative explanations for such anomalous diffusion were tested, and it was concluded that they did not play a significant role in the dynamic properties of the composites. It was proposed that the existence of the two relaxation rate constants (k r 2 ≈ 8 × 10-3 min-1, k r 1 = variable) could be related to mutually independent PAA and cross-linked PVA backbone relaxation, respectively.