  Since lattice strain and charge density affect various material properties of
graphene, a reliable and efficient method is required for quantification of the
two variables. While Raman spectroscopy is sensitive and non-destructive, its
validity towards precise quantification of chemical charge doping has not been
tested. In this work, we quantified in-situ the fractional frequency change of
2D and G peaks in response of charge density induced by sulfuric acid solution
as well as native lattice strain. Based on the experimental data and
theoretical corroboration, we presented an optical method that simultaneously
determines strain and chemically-induced charge density for three popular
excitation wavelengths of 457, 514 and 633 nm. In order to expedite
intercalation of dopant species through the graphene-SiO2 substrates, dense
arrays of nanopores were precisely generated in graphene by thermal oxidation.
The nano-perforated graphene membrane system was robust for multiple cycles of
doping and undoping processes, and will be useful in studying various types of
chemical interactions with graphene.
