Probe beam deflection technique

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... 

Probe Beam Deflection Method, Fig. 2 Experimental setup for probe beam deflection techniques... 

Barbero CA (2005) Ion exchange at the electrode/ electrolyte interface studied by probe beam deflection techniques. Phys Chem Chem Phys 7 1875-1884... 

Abrantes and Correia [622] employed the probe beam deflection technique to investigate the early stages of growth of poly(3-methylthiophene) and PPy. Their results support the assumption (in eontrast to the bulk of the reports published so far) that oligomer formation is not determinant for PPy deposition, quite in contrast to the formation of the thiophene-based polymer. 

Chung, K.Y. and Kim, K.-B. (2002) Investigation of structural fatigue in spinel electrodes using in situ laser probe beam deflection technique. J. Electrochem. Soc., 149 (1), A79. 

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]. 

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]. 

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

We have developed a laser beam deflection technique which, although similar to the method employed by Amer s group, differs in several important respects. U4-15) In particular, our method employs highly focused heating and probe laser beams, both incident normal to the sample surface, and the experiments are performed at high modulation frequencies of up to 10 MHz. 

The quartz crystal nanobalance (QCN) can be combined with practically any electrochemical methods, such as cyclic voltammetry, chronoamperometry, chronocoulometry, potentiostatic, galvanostatic, rotating disc electrode [11], or potentiometric measurements. The EQCN can be further combined with other techniques, e.g., with UV-Vis spectroscopy [12], probe beam deflection (PBD) [13], radiotracer [14], atomic force microscopy (AEM) [15], and scanning electrochemical microscopy (SECM) [16]. The concept and the instrumentation of... 

Probe-beam deflection is a technique in which a monochromatic source, typically a He-Ne laser beam, passing parallel to the electrode surface, is used to monitor refractive index changes in the diffusion layer. It is a simple and cost-effective way of profiling the diffusion layer, and is used to monitor the diffusion layer ingress and egress of ions, particularly protons. It is often used in conjunction with electrochemical quartz crystal microbalance (EQCM) measurements that monitor mass changes within or on the electrode layer itself. 

The application of combinations of electrochemical methods with non-electro-chemical techniques, especially spectroelectrochemistiy (UV-VIS, FITR, ESR), the electrochemical quartz crystal microbalance (EQCM), radiotracer methods, probe beam deflection (PBD), various microscopies (STM, AFM, SECM), ellipsometiy, and in situ conductivity measurements, has enhanced our understanding of the nature of charge transport and charge transfer processes, stmcture-property relationships, and the mechanisms of chemical transformations that occur during charg-ing/discharging processes. 

EQCM has also been combined with other techniques, such as probe beam deflection [193], scanning tunneling microscopy [233], scanning electrochemical microscopy [234, 235], and UV-VIS spectroelectrochemistry [236, 237], EQCM was also used under an alternative regime, ac electrogravimetry, which allows the fluxes of different ions taking part in the charge compensation process to be separated [43,98,99,107,108,184,205,238-242]. 

The probe beam deflection (PBD) technique (optical beam deflection or the mirage technique) is based on the measurement of refractive index gradients in front of the electrode I electrolyte interface [10,155,193,261-281]. 

The application of combined electrochemical and nonelectrochemical techniques, such as piezoelectric microgravimetry atEQCM [10,40,73,74,132,134,139-144], radiotracing [27,145], various spectroscopies [16,44,72,100,116,117,146] and microscopies [19,29,46,79,97,114,127,147,148], ellipsometry [15,21,26,86], conductivity [80], and probe beam deflection [149], has allowed irs to gain very detailed insights into the nature of electropolymerization and deposition processes, and so the production of conducting polymers, polymeric films, and composites with desired properties is now a well-established area of the electrochemical and material sciences. 

The results obtained by different techniques (radiotracer [121,126], quartz crystal microbalance [22,118-120,122-124,130-132,148-162], probe beam deflection [128, 131, 143, 164], STM [146], SECM [147], etc.) have revealed that the situation may be even more complicated than this. It has been found that the relative contributions of anions and cations to the overall ionic charge transport process depend upon several factors, such as the oxidation state of the polymer (potential), the composition of the supporting electrolyte, and the film thickness [2,19,22,23,118-132,148,150,162,164]. The latter effect is shown in Fig. 6.16. 

The results obtained by different techniques (radiotracer [80, 84], quartz crystal microbalance [73-76, 78, 83, 85-87, 90, 92-110], probe beam deflection (PBD) [88-90], etc.) have revealed that the situation may further be complicated. It has... 

Calvo and Etchenique summarized in their review some further in situ combinations of EQCM with non-electrochemical techniques (see [35] and references therein). For example, EQCM was also combined with ellipsometry in order to study the nucleation and growth of polyaniline films (reference 24 in [35]) or the viscoelastic behavior of poly(7-methyl-L-co y-n-octadecyl-L-glutamate) [17]. EQCM was combined with UV-visible absorption spectroscopy, in order to investigate the redox reactions of viologens. A combination of EQCM and probe beam deflection, PBD, was also reported in the literature (references 29, and 30 in [35], and [81]). PBD can discriminate between anion, cation, and solvent fluxes that might be generated on the electrode surface. 

Henderson Ml, Hillman AR, Vieil E, Lopez C (1998) Combined electrochemical quartz microbalance (EQCM) and probe beam defection (PBD) validation of the technique by a study of silver ion mass transport. J Electroanal Chem 458 241-248 Henderson MJ, Hillman AR, Vieil E (1999) Ion and solvent transfer discrimination at a poly(o-toluidine) film exposed to HC104 by combined electrochemical quartz crystal microbalance (EQCM) and probe beam deflection (PBD). J Phys Chem B 103 8899-8907 Henderson MJ, French H, Hillman AR, Vieil E (1999) A combined EQCM and probe beam defection study of salicylate ion transfer at a polypyrrole modified electrode. Electrochem Solid State Lett 2(12) 631-633... 

Planes GA, Miras MC, Barbero CA (2005) Double layer properties of carbon aerogel electrodes measured by probe beam deflection and AC impedance techniques. Chem Commun 2146-2148... 

---