Tip-Enhanced Photoinduced Electron Transfer and Ionization on Vertical Silicon Nanowires

Abstract

Nanostructured semiconductors are one of the most potent candidates for matrix-free laser desorption/ionization mass spectrometric (LDI-MS) analysis of low-molecular-weight molecules. Herein, the enhanced photoinduced electron transfer and LDI on the tip of a vertical silicon nanowire (SiNW) array were investigated. Theoretical simulation and LDI detection of indigo and isatin molecules in negative ion mode revealed that the electric field can be enhanced on the tip end of SiNWs, thereby promoting the energy and electron transfer to the analytes adsorbed on the tip of SiNWs. On the basis of this finding, a tip-contact sampling method coupled with LDI-MS detection was established. In this strategy, the tip of SiNWs can be regarded as microextraction heads for the sampling of molecules when they come in contact with analytes. Impression of skin, tissue, and pericarp on the vertical SiNW array can effectively transfer endogenous metabolites or exogenous substances onto the tip. Upon laser irradiation, the adsorbed molecules on the SiNW tip can be efficiently ionized and detected in negative ion mode because of the tip-enhanced electron transfer and LDI effect. We believe this work may significantly expand the application of LDI-MS in various fields.

High-Throughput Salivary Metabolite Profiling on an Ultralow Noise Tip-Enhanced Laser Desorption Ionization Mass Spectrometry Platform for Noninvasive Diagnosis of Early Lung Cancer

“…The platform displayed a high sensitivity and ultralow noise in LMW region. 20,21 With the ultralow noise TELDI-MS platform, salivary metabolites could be sensitively and reliably profiled in a high throughput way. 20 Another challenge in the salivary metabolic analysis is the variation in secretion volume caused by different water consumptions and other physiological and pathophysiological factors, which inversely affects metabolite concentration.…”

“…Nevertheless, the platform could be severely suffered from the matrix interference in the low-molecular weight (LMW) region, especially for the metabolite with a molecular weight below 400 Da. , Our previous work has developed a tip-enhanced laser desorption/ionization (TELDI) platform using fluorinated ethylene propylene polymer (FEP)-coated vertical silicon nanowire (VSiNW) arrays. The platform displayed a high sensitivity and ultralow noise in LMW region. , With the ultralow noise TELDI-MS platform, salivary metabolites could be sensitively and reliably profiled in a high throughput way …”

Ultrasensitive and High Reproducible Detection of Urinary Metabolites Using the Tip–Contact Extraction Method Coupled with Negative LDI-MS

“…To meet the needs of rapid, sensitive, and reproducible detection, our group has reported a tip-enhanced laser desorption ionization mass spectrometry based on vertical silicon nanowires (VSiNWs), which can significantly enhance the electric field and electron transfer at the tip of VSiNWs. , In addition, ultra-low background noise in low-molecular weight region (<400 Da) could be achieved after coating fluorinated ethylene propylene on the VSiNW array (FEP@VSiNWs) . With the assistance of the tip-enhanced LDI-MS platform, metabolic analysis of saliva samples has been successfully achieved .…”

Zirconia Hybrid Nanoshells for Nutrient and Toxin Detection

“…With the development of nanotechnology, the recently developed nano‐assisted laser desorption/ionization (LDI) MS has been preferred as a practical tool for analysis of small molecules, using metal, [ 11 ] metal oxide, [ 12 ] silicon, [ 13 ] carbon [ 14 ] nanoparticles as matrices. However, the lack of an ideal nanomaterial‐based matrix has prevented the wide adoption of this technique for general applications, which should possess unique electronic band structure for photoinduced electron transfer, [ 13a,15 ] rough surface morphology to trap small analytes, [ 16 ] low heat dissipation to facilitate thermal‐driven desorption, [ 17 ] specific chemical probes for selective capture and enrichment of trace analytes, [ 6a,18 ] and low preparation costs for large‐scale industrial application. [ 19 ] Therefore, core‐shell hybrids may serve as better matrices for LDI MS, by combining all of the above merits.…”