A compact, low-cost and high sensitive LIF based on pinhole metal-capillary and direct laser-diode excitation

For laser-induced fluorescence (LIF), the SNR and related concentration detectability was severely limited by background signal (noise). Herein, an axial-excitation LIF based on pinhole metal-capillary (PMC) and direct laser-diode excitation was proposed. An overall ~480 fold improvement on SNR was realized, because the laser-sidewall interaction ( LSI ) and related background signal (noise) can be effectively suppressed in PMC by avoidance of laser leakage and laser contact with capillary sidewall. For rhodamine B detection without sample enrichment, a detection limit of concentration (DLC) of 0.4 pM was obtained, which is 2.5 fold lower than the DLC (1 pM) of commercial LIFs equipped with bulky and expensive Ar + laser. For selective detection of Cu 2+ , a DLC of 5 pM was realized, which is more than 40 fold lower than that of previous fluorimetry detection with similar quantum-dot probe. The PMC-LIF features compact (16 × 4 × 4 cm 3 ), low-cost and high concentration detectability.