Interkalation

Interkalation, also spelled intercalation, is a chemical process in which guest species such as atoms, ions, or molecules are inserted between layers of a solid host material without significantly disrupting the host’s overall structure. The process is common in layered materials where planes are held by van der Waals or ionic bonds, creating galleries that can accommodate guests. The insertion is often reversible, allowing deintercalation and exchange of guests.

In inorganic chemistry and materials science, graphite intercalation compounds form when species insert between graphite layers; lithium-graphite intercalation is fundamental to lithium-ion batteries. Other hosts include transition metal oxides, layered sulfides, and clays such as montmorillonite. In these systems, intercalation often expands the interlayer distance and can involve charge transfer, changing electrical conductivity, electrochemical potential, and structural staging (stage 1, stage 2, etc.).

In biology and medicine, intercalation refers to the insertion of planar molecules between base pairs of DNA. DNA intercalators, such as ethidium bromide and doxorubicin, wedge between stacked nucleobases, affecting replication and transcription; they are used as stains and as therapeutic agents but can be mutagenic or cytotoxic.

Applications include energy storage, catalysis, and environmental remediation for materials intercalation, and in biology, diagnostic staining and cancer therapy for molecular intercalators. The term highlights a broad class of insertion processes based on layered hosts and guest molecules, with properties governed by host structure, guest size, charge, and chemistry.