Impact of Congo red dye in nano-porous silicon as pH-sensor

The combination of nano-porous silicon (nPS) with Congo red (CR) represents a nano-porous matrix which offer broad avenue of new and interesting properties depending on the involved materials as well as their morphology. Chemical route was utilized as the host material to achieve pores filling. They were impregnated with Congo red, which gave good results for the porous silicon as a promising pH sensor. The behavior of (nPS/CR) pH sensor, transformation of color (red-blue), is reversible after exposure to NH3 vapors, (red-blue-red). The ON/OFF behavior of the composite material depends upon the chemical processes occurring inside the pores. The fabrication of (nPS/CR) pH sensor depends on several factors {CR concentration, solvent type, and the chemical mechanism of CR adsorption on PS}.