The chapter discusses the near-infrared (NIR) absorption spectra of both pristine HIPCO (Heterostructured Iron Phosphide Cobalt Oxide) tubes and HIPCO-modified tubes. The analysis provides insights into the structural and chemical changes induced by the modification process, which can be crucial for understanding the optical and electronic properties of these materials.The chapter discusses the near-infrared (NIR) absorption spectra of both pristine HIPCO (Heterostructured Iron Phosphide Cobalt Oxide) tubes and HIPCO-modified tubes. The analysis provides insights into the structural and chemical changes induced by the modification process, which can be crucial for understanding the optical and electronic properties of these materials.