A novel matrix-assisted laser desorption/ionization time-of-flight mass spectrometric method (MALDI-TOF MS) for determination of highly sensitive small molecular compounds was developed based on molybdenum disulfide nanosheets hybridized with ultrathin graphitic carbon nitride (MoS 2 /g-C 3 N 4 ) as the matrix. With this approach, the synergistic effects of MoS 2 and g-C 3 N 4 enhance the UV absorption of MoS 2 /g-C 3 N 4 , increase both desorption and ionization efficiency in LDI MS, and induce higher signal-to-noise ratio of analytes when compared with the bare MoS 2 and g-C 3 N 4 matrix in the determination of amino acids, antibiotics, neutral oligosaccharides, uric acid, and polyethylene glycols (PEGs). The detection limits of these small molecular compounds are in the ranges 0.1 to 10 μg mL −1 , 1*10 −3 to 1.0 μg mL −1 , 1.0 to 10 μg mL −1 , and 2*10 −4 μg mL −1 , respectively, and the polydispersity index of these PEGs is less than 1.02. Moreover, high salt tolera`nce and homogeneous deposition on the spot results in good reproducibility. The relative standard deviations (RSDs) of shot-to-shot and spot-to-spot ( n = 15) of these compounds are less than 10.1% and 12.5%, respectively. With MoS 2 /g-C 3 N 4 , the uric acid in complicated biological samples can be directly determined in combination with LDI-TOF MS. Graphical abstract
We synthesized MoS 2 /g-C 3 N 4 nanohybrid as an efficient matrix for MALDI-TOF MS analysis of small molecules as well as quantitative detection of uric acid in human urine.
Constructing a 0D/3D p–n heterojunction is a feasible strategy for accelerating photo-induced charge separation and promoting photocatalytic H2 production. In this study, a 0D/3D MoS2/g-C3N4 (0D/3D-MCN) photocatalyst with a p–n heterojunction was prepared via a facile light-assisted deposition procedure, and the 3D spongy-like g-C3N4 (3D-CN) was synthesized through simple thermolysis of NH4Cl and melamine mixture. For comparison, 2D-MoS2 nanosheets were also embedded in 3D-CN by a solution impregnation method to synthesize a 2D/3D-MCN photocatalyst. As a result, the as-prepared 0D/3D-MCN-3.5% composite containing 3.5 wt% 0D-MoS2 QDs exhibited the highest photocatalytic H2 evolution rate of 817.1 μmol h−1 g−1, which was 1.9 and 19.4 times higher than that of 2D/3D-MCN-5% (containing 5 wt% 2D-MoS2 nanosheets) and 3D-CN, respectively. The results of XPS and electrochemical tests confirmed that a p–n heterojunction was formed in the 0D/3D-MCN-3.5% composite, which could accelerate the electron and hole movement in the opposite direction and retard their recombination; however, it was not found in 2D/3D-MCN-5%. This study revealed the relationship among the morphologies of MoS2 using g-C3N4 as a substrate, the formation of a p–n heterojunction, and the H2 evolution activity; and provided further insights into fabricating a 3D g-C3N4-based photocatalyst with a p–n heterojunction for photocatalytic H2 evolution.
危险品化学品经营许可证（带存储）