Operando laser scattering: probing the evolution of local pH gradients on complex electrode architectures

Abstract Self-assembly, complexation, agglomeration and precipitation phenomena relevant to biological, electrocatalytic and technological processes are strongly influenced by changes of the local pH at the solid-liquid interfaces where they occur. Understanding proton dynamics in the diffusion layers generated by these processes is of prime importance to improve their diagnosis and enable modelling and better control over them. Here we introduce a non-invasive pH-sensing approach that is based on the Tyndall effect enhancement modulated by pH-controlled agglomeration events. Using metal electrodeposition for advanced semiconductor wiring technology as a test vehicle, we demonstrate that our proposed strategy simultaneously provides real-time visualization of the pH dynamics and pH-guided reactivity with high spatial resolution without physically or chemically influencing the investigated surfaces. We suggest that its applicability can be universally extended to other relevant nanoaggregation/decomplexation processes occurring at light-addressable interfaces provided the probed colloids are smaller than the wavelength of visible light.