Selective Pt-deposited TiO2 nanomatrices for enhanced SALDI-TOF MS detection of small molecules

Selective Pt deposition on TiO 2 effectively regulates photogenerated charge separation in MALDI-TOF MS nanomaterial matrices. • Photogenerated holes dominate positive ion mode, while electrons dominate negative, governing small-molecule ionization. • Carrier-dominated mechanism is validated in complex TiO 2 , enabling sensitive detection of representative pollutants. Surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF MS) has emerged as a powerful technique for small-molecule analysis with the introduction of inorganic nanomaterial matrices. However, its analytical performance remains highly dependent on matrix-analyte interactions, and a unified mechanistic understanding is still lacking. Here, we demonstrate that selectively deposited Pt/TiO 2 nanomatrices significantly enhance SALDI-TOF MS performance by regulating photogenerated charge carrier dynamics. Facet- and phase-selective Pt deposition promotes the spatial separation and directional migration of photogenerated electron-hole pairs, leading to pronounced signal enhancement in both positive and negative ion modes. Using amino acids as model analytes, facet-selective Pt/TiO 2 affords up to 3.4-fold enhancement for [A + K] + in the positive ion mode and 3.3-fold for [A-H] − in the negative ion mode, outperforming pristine TiO 2 and nonselectively deposited Pt/TiO 2 counterparts. Photo/electro-chemical analyses, including transient photocurrent, electrochemical impedance spectroscopy, and photoluminescence, correlate enhanced charge carrier separation with improved SALDI-TOF MS performance. Scavenger experiments further reveal that photogenerated holes play a dominant role in adduct formation in the positive ion mode, whereas photogenerated electrons govern analyte deprotonation in the negative ion mode. The proposed mechanism is validated in the structurally complex Pt/commercially available TiO 2 (Pt/P25) system via phase-selective Pt deposition, demonstrating its generality. Furthermore, the optimized Pt/TiO 2 matrix achieves sensitive detection of environmental pollutants, including antibiotics and bisphenol A (BPA), achieving a detection limit of 0.1 ppm. This study establishes a clear charge carrier-dominated mechanism for SALDI-TOF MS nanomatrices, provides rational guidance for the design of high-performance matrices, and highlights their practical potential in environmental pollutant analysis. Download: Download high-res image (107KB) Download: Download full-size image