Characterization of Sol-Gel Derived Composite Silica Carbon Electrodes

Abstract

Sol-gel derived composite silica-carbon electrodes exhibit favorable electrochemical characteristics. The electrodes benefit from the conductivity and electrochemical advantages of the carbon powder, from the favorable properties of the ceramic network and from the versatility of the sol-gel process. Hydrophobie composite electrodes reject water, only their outermost surface is wetted and they exhibit good signal to background currents. A comparison of several types of carbon powders reveals that higher carbon loading and larger surface area electrodes can be attained by incorporation of dense graphite powder. When high surface area, small size carbon-black powder is used, a homogeneous distribution of microelectrodes, separated by insulating modified silica is formed. This ensemble of microelectrodes increases the sensitivity of the CCEs by more than two orders of magnitude as compared to glassy carbon electrode and graphite CCEs.

Analytical Applications of Silica-Modified Electrodes -A Comprehensive Review

“…Composite carbon-silicate electrodes, also called ceramic carbon electrodes (CCEs), were introduced, then developed and largely used by Lev's group [65,[172][173][174][175]. CCEs are made of a sol-gel derived porous glass network containing a homogeneous distribution of carbon powder.…”

“…Both hydrophilic and hydrophobic glasses can be obtained, by selecting the appropriate precursors: tetraalkoxysilanes in the first case and alkyl-or phenyl-trialkoxysilanes in the second case. Interestingly, the hydrophobic composite ceramics exhibit good signal to background current ratios because they reject water, allowing only their outermost surface to be wetted by the surrounding electrolyte solution [173]. Compared to carbon paste electrodes, CCEs are robust, offer higher stability and can be moulded in a large variety of configurations (monolithic rod, coated layers or flat sheets, microelectrode arrays).…”

“…Their scope of applications includes various indicator electrodes which can be modified by either organic or inorganic species (by covalent bonding, doping or impregnation), as well as immobilization supports for biomolecules [172]. When using an appropriate carbon source (acetylene black or Ketjenblack), the hydrophobic CCEs exhibit very good electroanalytical performances, with a 200-fold increase in the sensitivity as compared to glassy carbon electrodes [173]. The voltammetric characteristics of CCEs were compared to other classes of graphite electrodes, by using various organic and inorganic redox couples, and it was concluded that CCEs show good stability and reproducible behavior in aqueous and mixed solvent media [174].…”

“…Ceramic-carbon electrodes (CCEs) were first introduced by Lev and co-workers [65,[172][173][174][175], so it is thus not surprising that the first ceramic-carbon bioelectrodes were also described by the same group in 1995 [274], and then largely applied and modified in order to extend their scope of applications [275][276][277][278][279][280][281][282]. Their works were motivated by the fact that sol-gel derived electrochemical biosensors suffer from the slow diffusion of organic species within the silicate matrix, resulting in excessively long response times [92,261,263,264,[283][284][285].…”

“…By combining the biosensing advantages of sol-gel carbon biocomposites [65,[172][173][174][175] with the electrocatalytic action of metal-dispersed particles [287][288][289], this new class of materials doped with GOD displayed a remarkable selectivity towards the glucose substrate together with a greatly enhanced sensitivity compared to the corresponding unmodified metal-ceramic electrode. Metals like ruthenium [293] and gold [294] were used to catalyze the detection of the enzymatically liberated hydrogen peroxide, allowing its electrochemical sensing in the optimal region (+0.1 to -0.1 V) where unwanted reactions do not occur.…”