Quartz microbalance technique

Recently, Feldmann and Melroy [131] utilized a quartz microbalance technique to simultaneously determine the net current and the partial anodic and cathodic currents in a single complete electroless copper bath. The cathodic current is calculated by converting the deposition rate measured with the microbalance into the unit of current, while the anodic current is computed by subtracting the cathodic current from the net current measured directly on the microbalance electrode. Using this technique, Feldmann and Melroy showed that the potential at which the reduction of the Cu-EDTA complex begins at 70 °C shifts by as much as 0.3 V in positive direction upon addition of formaldehyde. It was also shown that at a given potential, the rate of copper deposition increases with increasing formaldehyde concentration (Fig. 23). The observed catalytic effect of formaldehyde is attributed to an interaction between formaldehyde and the Cu-EDTA complex, possibly to the formation of Cu(EDTA)/formaldehyde complex. However, the detailed mechanism of this catalytic effect has not been clarified. 

Fig. 7. Typical growth curves of a CdS CBD film measured in situ by the quartz microbalance technique (small open symbols). Filled symbols correspond to ex situ thickness measurements with a profilometer. (a) Growth of a compact layer with thickness saturation, dotted line shows the initial linear regime, conditions [Cd]T = 0.014 M, [TU] = 0.14 M, [NHa] = 1.74 M, T = 60 °C. (b) overgrowth of a porous poorly adherent layer towards long deposition times, same conditions as (a) but with [TU] = 0.03 M.

Zar bska K, Skompska M (2011) Electrodeposition of CdS from acidic aqueous thiosulfate solution— invesitigationof the mechanism by electrochemical quartz microbalance technique. Electrochim Acta 56 5731... 

Despite H/D kinetic isotope studies, application of modern techniques such as atomic force microscopy (AFM), electrochemical mass spectrometry (EMS) [60], and electrochemical quartz microbalance (EQCM), the mechanism of electroless nickel and cobalt, whatever reducing agent is involved, continues to be the subject of much discussion and varying opinions. 

Endres et al. [82] have demonstrated the suitability of an air- and water-stable ionic liquid for the electropolymerization of benzene. This synthesis is normally restricted to media such as concentrated sulfuric acid, liquid SO2 or liquid HF as the solution must be completely anhydrous. The ionic liquid used, l-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate, can be dried to below 3 ppm water, and this ionic liquid is also exceptionally stable, particularly in the anodic regime. Using this ionic liquid, poly(para-phenylene) was successfully deposited onto platinum as a coherent, electroactive film. Electrochemical quartz crystal microbalance techniques were also used to study the deposition and redox behavior of the polymer from this ionic liquid (Section 7.4.1) [83]. 

Su X, Wu Y-J, Knoll W (2005) Comparison of surface plasmon resonance spectroscopy and quartz crystal microbalance techniques for studying DNA assembly and hybridization. Biosens Bioelectron 21 719-726... 

The electrochemical reduction of Ti02 is known to be accompanied by the intercalation of small cations. This finding has been explored in sensitizing anatase films for battery applications [149]. Cation coordination to titanium alkoxide sol-gel precursors is also well known [150]. Lyon and Hupp used quartz crystal microbalance techniques to determine the mass of intercalating cations as the TiOa film is reduced [151]. Hagfeldt and co-workers have studied Li+ and Na intercalation into anatase Ti02 both theoretically and experimentally [152, 153). They found that the diffusion constants for Li and Na+ are temperature dependent with an activation barrier of 0.4 eV for insertion and 0.5 eV for extraction. The Li+ diffusion coefficient at 25 °C into the nanoporous structure was approximately 2 X 10 cm s for insertion and 4 x 10 cm s for extraction. 

INVESTIGATION OF HORSERADISH PEROXIDASE ADSORPTION ON GOLD AND POLYSTYRENE SULFONATE MODIFIED SURFACES BY QUARTZ CRYSTAL MICROBALANCE TECHNIQUE... 

K. T. Lee and S. Raghvan, Etch rate of silicon and silicon dioxide in ammonia-peroxide solutions measured by quartz crystal microbalance technique, Electrochem. Solid State Lett. 2, 172, 1999. 

Two additional electrochemical techniques, electrochemical quartz microbalance, EQCM and scanning atomic force electrochemical microscopy, can be mentioned. EQCM is based on the piezoelectric properties of quartz and permits the user to evaluate mass changes occurring on an electrode supported over a quartz lamina. 

This variation is one of the reasons why other investigations have applied a quartz microbalance (QMB) [63, 176] technique to measure the threshold with a much higher precision. As an alternative technique, conventional UV spectroscopy is used in this study to determine the ablation threshold with single pulses. The absorbances of thin polymer films cast on quartz wafers were measured before and after irradiation with various fluences, as shown in Fig. 24. 

Abstract In this chapter we focus on the application of the piezoelectric-based quartz crystal microbalance (QCM) technique to create and study thin polymeric films. The electrochemical variant of the quartz crystal microbalance technique (EQCM) allows one to study changes in the interfacial mass and physical properties associated with electron transfer processes occurring at the electrode surface, such as those accompanying... 

During the oxidation of formic acid and formaldehyde on platinum electrodes, an oscillatory behavior is frequently observed. " The surface poisoning species play a central role in the triggering of the oscillatory phenomena. Recent studies on formic acid and formaldehyde oxidation confirm this view. Inzelt and Kert sz reported that by the use of electrochemical quartz crystal microbalance technique (EQCM), the periodical accumulation and consumption of strongly bound species can be observed in the course of potential oscillation produced by the galvanostatic oxidation of formic acid. 

These values were obtained by quartz crystal microbalance technique. 

Monometallic systems based on Pt, Pd, Rh, Co, Cu, and also some bimetallic systems, Pt-Ag, Pt-Sn, Pd-Rh, Pt-Pb, have been developed, using a similar electrochemical deposition process [48-55]. Due to its important electrocatalytic behaviour, particles of platinum were mainly considered [48,54-66], but also bimetallic Pt-based systems, such as Pt-Ag [46], Pt-Ru [67-69] and Pt-Sn [53,68-70]. Dispersion of palladium particles was also carried out [47,71-73] and bimetallic Pd-Rh and Pd-Pt particles were also obtained [74], Deposition of nickel and copper into polypyrrole films from standard plating baths was considered recently, and observed by the Electrochemical Quartz Crystal Microbalance technique [75,76]. 

Hierlemann A., Weimar U., Kraus G., Gauglitz G., and Gopel W., Environmental chemical sensing using quartz microbalance sensor arrays Application of multicomponent analysis techniques. Sens. Mater., 1, 179-189, 1995. 

It has been shown that the TEA process leads to high-quality films [43—45]. The mechanism involving the CBD of CdS thin films from the ammonia-thiourea system have been studied in situ by means of the quartz crystal microbalance technique (QCM) [25]. The formation of CdS was assumed to result from the decomposition of adsorbed thiourea molecules via the formation of an intermediate surface complex with cadmium hydroxide. This mechanism is different from the dissociation mechanism involving the formation of free sulfide ions in solution, and which had previously been reported [46-49]. Thus, the influence of growth parameters such as bath temperature, deposition rate, bath composition, etc., on various film properties has been studied [37, 39, 41, 50, 51], and the main parameters which determine the quality of the films were deduced. The chemical deposition of CdS thin films generally consisted of the decomposition of thiourea in an alkaline solution containing a cadmium salt The deposition process was based on the slow release of Cd and S ions in solution which then condensed on an ion-by-ion basis on the substrate. The reaction process for the formation of CdS may be described by the following steps [25, 35, 36, 43, 52-54]. 

AUB Arrbert, J.H., Solrrbility of carbon dioxide in polymers by the quartz crystal microbalance technique,/. Supercrit. Fluids, 11, 163, 1998. 

Cyclic voltammetric studies of these metallodendrimers showed one reversible oxidation wave, characteristic of independent, non-interacting redox centers. Also, the use of these materials for the modification of electrode surfaces was explored [37-39]. The researchers found that platinum, glass, and carbon-disk electrodes modified by electrodeposited films of these dendrimers are extremely durable and reproducible, with no detected loss of electroactivity even after their use in different electrolyte solutions or after standing for long periods in air. Studies on the thermodynamics and kinetics of adsorption of these redox-active dendrimers onto Pt electrodes by means of electrochemical and electrochemical quartz crystal microbalance techniques were conducted. These showed the adsorption processes to be activation-controlled rather than diffusion-controDed, and to be dependent on... 

M. Hepel, X. M. Zhang, R. Stephenson, S. Perkins, Use of electrochemical quartz crystal microbalance technique to track electrochemiccJly assisted removal of heavy metals from aqueous solutions by cation-exchange composite polypyrrole-modified electrodes. Microchem J 1997, 56 (1), 79-92. 

Quartz Microbalance and Direct Microbalance Techniques. These methods provide direct measurements of the adsorbed mass. The vibration frequency of a quartz single crystal is very sensitive to the mass of the crystal. Upon adsorption, the vibration frequency shifts to lower values and the changes in the frequency can be related to the adsorbed mass. The surface excess can be determined by dividing the adsorbed mass by the surface area (6). Another method to directly measure the surface excess is the microbalance technique. In this technique, the... 

The electrochemical quartz microbalance (EQCM) is a powerful measuring technique commonly used by electrochemists as weU by scientists coming from other fields, like physicists and biologists. One can find descriptions of the EQCM technique and of its applications in textbooks dealing with fundamentals of electrochemistry [1 ]. This fact proves the importance of this technique within the electrochemical scientific community. 

Mecca VM, Carlsson JO, Bucur RV (19%) Extensions of the quartz-crystal-microbalance technique. Sens Actuat A 53 371-378... 

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