Nucleation of Tetrakis(4-chlorophenyl)borate at micro liquid-liquid interface

Abstract Micro Interface between Two Immiscible Electrolyte Solutions (micro-ITIES) has a sensitive detection capability and is suitable for measuring the fast kinetics of charge transfer according to its low IR drop and charging current. In most previous studies, some of extra hydrophobic salts including tetrakis(4-chlorophenyl)borate, tetrakis(pentafluorophenyl)borate and tetraphenylborate were often used as organic electrolytes as they were hardly transfer into aqueous solution and then provide a sufficiently stable potential windows. However, in this manuscript, it was discovered that intense spike-liked current signals appeared at high potential when hydrochloric acid and tetrakis(4-chlorophenyl)borate were served as the water and 1,2-dichloroethane phase electrolyte, respectively. The exceptional current spikes might belong to the heterogeneous nucleation at the interface, which surely interfered with related analysis on interface, i.e. single nano entity detection. Thus, the potential factors, which might affect the nucleation on micro-ITIES, including interface diameter, concentration and applied potential were investigated to prove that the current spikes were induced by the collision of nuclei produced by contact of hydrogen ion from aqueous phase and tetrakis(4-chlorophenyl)borate from organic phase. Moreover, lithium ion and potassium ion were also found to nucleate with tetrakis(4-chlorophenyl)borate at the positive end of potential window. In general, the potential nucleation problem on micro-ITIES was revealed and it was also suggested that appropriate conditions to avoid heterogeneous nucleation caused by ion transfer reaction of supporting electrolytes should be chosen for other researchers.