One-step fabrication of high-density Si nanotips as SALDI-MS substrate for highly sensitive detection

Abstract

The high sensitivity of surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) analysis depends on the enhancement of the signal intensity and the reduction of the background. Here, high-density Si nanotips were prepared as SALDI-MS substrate by taking template-free reactive ion etching for sensitive detection. The high-density Si nanotips act as tiny antennas to concentrate the laser energy and generate photo-induced electrons on a small area, which promotes desorption and ionization of molecule, enhancing the signal intensity. Additionally, the high stability of Si nanotips under laser irradiation ensures low background interference. The applicability of the substrate was demonstrated by the detection of various small molecules, e.g., fatty acids, amino acids, environmental pollutants and drugs. In addition, this substrate can be successfully applied for detecting trace small molecules in complex sample, such as 10−9 M verapamil in serum and 10−12 M crystal violet in lake water. Moreover, the banned fungicides left on the fish skin was also detected. The substrate is compatible with imaging, and the endogenous and exogenous substances in fingerprint were visualized by MS imaging. These results demonstrate the easily prepared high-density Si nanotips SALDI-MS substrate is of high detection sensitivity and great value toward large-scale practical applications.