C1s

C1s refers to the photoelectron signal arising from the carbon 1s core level in X-ray photoelectron spectroscopy (XPS). It is a principal feature in spectra of materials containing carbon, including organic compounds, polymers, carbon-based materials, coatings, and biological samples analyzed on various substrates.

In XPS, the C1s binding energy is typically in the range of about 284 to 290 eV. The commonly used anchor is around 284.8 eV, corresponding to carbon in C–C and C–H environments (adventitious carbon on many samples provides this reference). Accurate interpretation often relies on charge-correction to this reference or to a calibrated standard.

The C1s peak is frequently deconvoluted into separate components that reflect different chemical states. For example, C–C/C–H bonds yield a peak near 284.8 eV; C–O bonds appear around 286.0–286.5 eV; C=O groups near 287–289 eV; and O–C=O groups around 289–290 eV. The relative intensities of these components provide information about surface composition and functionalization.

Practical considerations include the surface-sensitive nature of XPS (sampling depth of a few nanometers) and potential charging of insulating samples, which can shift peak positions. Charge compensation and careful calibration to the C1s reference are important for reliable analysis. Adventitious carbon, if present, can complicate interpretation but also serves as a convenient internal standard.

Applications of C1s analysis span polymers, coatings, carbon materials (graphene, carbon nanotubes), photovoltaics, batteries, and biomedical surfaces, where carbon functionality and oxidation state are key.