Aging Investigation on Optical Characteristics of Copper Sulfide Bio-Templated Nanowires
Authors:Gabriel Grajeda, Shahriar Zaman
Mentor:Elaine Haberer, Assistant Professor, Electrical Engineering Department, University of California, Riverside
With global energy consumption increasing rapidly, low-cost and efficient renewable energy technologies are in high demand. Solar energy is of particular interest, being a plentiful yet underutilized form of renewable energy. Efficient solar cells must absorb a large fraction of the incident light, and extract the energy in the form of electrical current. Some nanoscale materials, which are known as strong optical absorbers, can absorb sunlight very effectively with very thin material layers. Copper sulfide is one such material. Upon exposure to sunlight, copper sulfide can generate significant electrical current. Abundant and non-toxic, it is well-suited for wide-spread use. However, reports indicate that nanoscale copper sulfide is not stable over long time periods, but rather changes in composition and phase with exposure to ambient conditions, diminishing the produced current. The decreased performance can be correlated to increased optical absorption in the near infrared (NIR) which is associated with localized surface plasmon resonance (LSPR). In Nature, biomolecules such as peptides and proteins have demonstrated the ability to stabilize some nanoscale materials. In this work, a biomolecule scaffold was used to synthesize nanoscale copper sulfide using liquid chemical precursors. The bio-templated material were dropcast onto glass slides, vacuum-dried, and aged at atmospheric temperature and pressure to form films. To investigate the stability imparted by the biomolecules, optical absorption was measured as a function of time in the NIR region of the spectrum using a UV/VIS/NIR spectrophotometer. The NIR absorption increased with prolonged ambient exposure conditions, indicating that the biomolecule template was insufficient to stabilize the synthesized material. The increase was attributed to rapid surface oxidation which could not be completely prevented by the surrounding biomolecules. Further studies are needed to better understand the extent to which, if any, biomolecule templates can inhibit nanoscale copper sulfide oxidation.