Probe beam deflection

A variety of other techniques have been used to investigate ion transport in conducting polymers. The concentrations of ions in the polymer or the solution phase have been monitored by a variety of in situ and ex situ techniques,8 such as radiotracer studies,188 X-ray photoelectron spectroscopy (XPS),189 potentiometry,154 and Rutherford backscatter-ing.190 The probe-beam deflection method, in which changes in the density of the solution close to the polymer surface are monitored, provides valuable data on transient ion transport.191 Rotating-disk voltammetry, using an electroactive probe ion, provides very direct and reliable data, but its utility is very limited.156,19 193 Scanning electrochemical microscopy has also been used.194... 

The development of hydrodynamic techniques which allow the direct measurement of interfacial fluxes and interfacial concentrations is likely to be a key trend of future work in this area. Suitable detectors for local interfacial or near-interfacial measurements include spectroscopic probes, such as total internal reflection fluorometry [88-90], surface second-harmonic generation [91], probe beam deflection [92], and spatially resolved UV-visible absorption spectroscopy [93]. Additionally, building on the ideas in MEMED, submicrometer or nanometer scale electrodes may prove to be relatively noninvasive probes of interfacial concentrations in other hydrodynamic systems. The construction and application of electrodes of this size is now becoming more widespread and general [94-96]. 

Figure 2.18 Probe-beam deflection oxidation transients for (a) positively capped (PAH-Os)i5(PSS)i4 and (b) negatively capped (PAH-Os)i5(PSS)i5 in 0.01 M HCI. Anion uptake/cation release appears as a positive/negative PBD signal. Taken from Ref. [150].

Figure 2.22 Chronoamperometric current transients (dotted lines) and probe-beam deflection transients (solid lines) during the oxidation-reduction cycles of (PAH-Os)t5(PSS)- 4 PEM film in 10 mM HCI solution. Panels A-D show consecutive oxidation-reduction steps with a wait time of 180 s at the end of each train in the reduced state. Taken from Ref. [28].

The process of Pb deposition depends on the presence of adsorbed species. On polycrystalline gold, in HCIO4 acid solutions, a combined quartz crystal microbalance and probe beam deflection methods have pointed to three stages of the process - (1) water molecules release from gold surface, (2) metal UPD associated with adsorbed OH ions replacement, followed by (3) water formation [274]. In the presence of adsorbed anions or organic... 

Pb UPD on polycrystalline An electrode in 0.1 M perchloric acid solution has been studied by Henderson et al. [484]. In this study, CV, electrochemical quartz crystal microbalance (EQCM), and probe beam deflection methods have been used. It has been found that Pb UPD proceeds in three steps. The first step comprised water ejection from the gold surface. This step was followed by metal UPD accompanied by the removal of the adsorbed OH. Also, Zeng and Bruckenstein have studied UPD and adsorption of Pb on pc-Au electrodes, applying XPS and TOF-SIMS method in case of 0.1 M NaCl electrolyte [485], and EQCM in case of 0.1 M NaCl04 and 0.1 M NaCl electrolytes [486]. In the presence of chloride anions, the adsorption of Pb—Cl complex has been found. 

Figure 7 Electrochemical photothermal deflection spectroscopy experiment (0.5 mol dm-3 Na2S04 pH = 10.5, 20 mV s 1), illustrating the detection of the onset of dissolution of nuclear fuel (U02) (A) voltammetric response for scans to various anodic potential limits (B) and (C) probe beam deflection for each scan. The deflection of the probe beam is proportional to the dissolved uranium concentration, and deflection of the probe beam towards the electrode surface is an indication that dissolution is occurring (Reprinted from Ref. 2 with permission from Elsevier Science S.A.)...

Chronodeflectometry (CD) — A - probe beam deflection method in which a - potential pulse is applied, usually from a potential where there is no reaction, to one where the reaction evolves completely to the formation of products. The time evolution of the deflection signal is sampled and plotted as a function of time, which is named chronodeflectogram [i]. 

Cyclic voltadeflectometry (CVD) — A -> probe beam deflection method in which a cyclic linear potential sweep is imposed to the working electrode at a constant -> potential sweep (or scan) rate (v) in order to obtain a deflection-potential curve denominated cyclic voltadeflectogram [i]. 

EQCM can be combined with other techniques, e.g., with -> probe beam deflection (PBD) [viii], radiotracer methods (- tracer methods) [ix], and - scanning electrochemical microscopy [x]. 

The term mirage effect has been indistinctly assigned to studies performed by - photothermal deflection spectroscopy (PDS) and - probe beam deflection (PBD). However, PDS is based on the analysis of the first term of the last equation, whilst in PBD, essentially the second term is evaluated. 

Optical beam deflection probe beam deflection... 

Probe beam deflection (PBD) — An in-situ electrochemical technique employed to study the mass fluxes... 

S. Cattarin, E. Decker, and D. Dini, Anodic silicon dissolution in acidic fluoride electrolyte. A probe beam deflection investigation, J. Phys. Chem. B 102, 4779, 1998. 

D. Dini, S. Cattarin, and F. Decker, Probe beam deflection study of p-Si electrodissolution in acidic fluoride medium in the oscillating regimes, J. Electroanal. Chem. 446, 7, 1998. 

The shortcomings of EQCM methods in investigating ion exchange processes were somewhat compensated by the probe beam deflection technique [248]. This technique is based on the measurement of the extent of deflection of a parallel laser beam passing over a polymer coated electrode surface at a very small distance. When there is an ion flux near the electrode... 

Measurements of the deflection of a light beam caused by local heating at the solid/solution interface as a function of the wavelength of light illuminating this interface are an alternative possibility the resulting method is called photothermal deflection spectroscopy (PDS) [127, 128]. The experimental setup as depicted in Fig. 5.30 closely resembles the arrangement for probe beam deflection studies treated in Sect. 5.1.9. 

Fig. 5.30. Probe beam deflection setup for photothermal spectroscopy [129]...

The term photothermal deflection is used as an equivalent to probe beam deflection the term optical beam deflection has been used only infrequently. 

Probe beam deflection can be observed during metal deposition and dissolution. The method is sensitive towards changes in the concentration gradient originating from dissolution or deposition of submonolayer amounts of material on the electrode surface [875]. A typical result of PBD measurements is displayed in Fig. 5.140. The negative PBD response observed during anodic stripping of the silver indicates concentration decay into the solution phase. The positive response... 

Fig. 5.139. Experimental setup for probe beam deflection studies...

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