Regulating the work function of Cu2O films via crystal facet engineering with enhanced charge transfer and SERS activity

Semiconductors have been extensively studied for SERS applications owing to the advantage of inexpensive, nontoxic and easy fabrication. However, the facile design of uniformity substrates with enhanced charge transfer and SERS activity are highly desirable. Herein, we reported the fabrication of Cu2O films with (100) and (111) facets exposed by adjusting the pH value of electrolyte. When using 4-NBT as probe molecule, the Cu2O(100) exhibits an improvement of enhancement factor about 2.7 times than Cu2O(111), as well as relatively low limit of detection up to 1 x 10(-7) M. All calculated relative standard deviation values are lower than 5 %, which demonstrates the uniformity and reproducibility of as-prepared Cu2O films. UPS analysis reveals that (100) facet possesses lower electron work function, and can promote the efficient interfacial charge transfer. Furthermore, First-principles calculation confirms that (100) facet possess the better adsorption ability for 4-NBT, which can transfer more electrons from Cu2O to the molecule due to its lower work function, and thus resulting in the remarkable improvement of SERS activity. This research will offer more choices for the design of uniformity semiconductor substrates with enhanced SERS sensitivity based on crystal facet engineering.

Automated summary

Cu2O films with (100) and (111) facets were fabricated by adjusting the pH value of the electrolyte. Cu2O(100) exhibited higher SERS activity and lower detection limit compared to Cu2O(111). (100) facet possessed lower electron work function and better adsorption ability for 4-NBT, resulting in efficient interfacial charge transfer and enhanced SERS activity.