Tianyan You

Nitrogen-Doped Graphene Quantum Dots@SiO2 Nanoparticles as Electrochemiluminescence and Fluorescence Signal Indicators for Magnetically Controlled Aptasensor with Dual Detection Channels

We proposed a facile method to prepare the nitrogen-doped graphene quantum dots (NGQDs) doped silica (NGQDs@SiO2) nanoparticles (NPs). The NGQDs@SiO2 NPs were further explored as a versatile signal indicator for ochratoxin A (OTA) aptasensing by combination with electrochemiluminescence (ECL) and fluorescence (FL) detection. In this strategy, the core-shell Fe3O4@Au magnetic beads (MBs) acted as a nanocarrier to immobilize the thiolated aptamer specific for OTA, and the amino modified capture DNA (cDNA) was efficiently tagged with NGQDs@SiO2 NPs. The multifunctional aptasensor was thus fabricated by assembly of the NGQDs@SiO2 NPs onto the surface of Fe3O4@Au MBs through the high specific DNA hybridization between aptamer and cDNA. Upon OTA incubation, the aptamer linked with Fe3O4@Au MBs preferred to form an aptamer-OTA complex, which resulted in the partial release of the preloaded NGQDs@SiO2 NPs. The more OTA molecules in the detection system, the more NGQDs@SiO2 NPs were released into the bulk solution and the less preloaded NGQDs@SiO2 NPs were accumulated on the magnetic electrode surface. This provided a dual channel for OTA detection by combination with the enriched solid-state ECL and homogeneous FL detection. The FL assay exhibits a wide dynamic range and is more reproducible due to the homogeneous detection while the ECL assay possesses a lower detection limit and is preferable by using a cheaper instrument. One can obtain a preliminary screen from FL assay and a more accurate result from ECL assay. Integrating the virtues of dual analytical modality, this aptasensing strategy well-balanced the rapidity, sensitivity, and dynamic range, making it promising to other targets with aptamer sequences.

Gold nanrods plasmon-enhanced photoelectrochemical aptasensing based on hematite/N-doped graphene films for ultrasensitive analysis of 17β-estradiol

It remains a vital task to establish ultrasensitive sensing interfaces for detection of target analytes to meet the demands of modern analysis. Herein, a highly sensitive turn-on photoelectrochemical (PEC) platform for trace 17β-estradiol (E2) assay was developed based on Au nanrods (AuNRs) with surface plasmon resonance (SPR) properties induced signal amplification. Specifically, a ternary hybrid was prepared by integrating hematite (α-Fe2O3) nanocrystals and N-doped graphene (NG) with AuNRs, which further served as highly efficient photoactive species. Subsequently, a PEC sensing platform was fabricated based on the specific binding of E2 and its aptamer. On such a sensor, the capture of E2 molecules by aptamers led to increased photocurrent. This was attributed to that the specific recognition reaction between E2 and aptamer resulted in the conformational change of the aptamers and complete dissociation of some aptamers on the PEC sensing interface. It can be confirmed by the electrochemical impedance spectroscopy (EIS) results. This process decreased the steric hindrances between the electrode surface and solution and thus increased the photocurrent response. Under the optimal conditions, the as-prepared PEC aptasensor exhibited superb analytical performances for detection of E2 in the range from 1×10-15M to 1×10-9M with a detection limit of 3.3×10-16M. The aptasensor manifested outstanding selectivity towards E2 when other endocrine disrupting compounds with similar structure coexisted. Furthermore, the aptasensor was successfully applied for the determination of E2 in milk powder. The present strategy provides a potential way to boost the activity of photoactive materials and improve the sensitivity of PEC biosensor.

Superior catalytic activity of Pt/carbon nanohorns nanocomposites toward methanol and formic acid oxidation reactions

Pt nanoparticle-loaded carbon nanohorns (Pt/CNHs) nanocomposites were synthesized by using formic acid as reducing agent at room temperature. Taking the advantage of the high surface area and excellent electronic conductivity, CNHs were used as support without any pretreatments for the enhancement of catalytic performance. By adjusting the feeding amount of H2PtCl6, the mass, size and distribution of Pt nanoparticles could be effectively controlled on CNHs. Compared with commercial Pt/C, the synthesized Pt/CNHs exhibit higher catalytic activity and improved long-term stability toward both methanol and formic acid oxidations. Among the Pt/CNHs, 13% wt. Pt/CNHs exhibit the best catalytic performances for the small size (2.4 nm) and uniform distribution of Pt NPs on CNHs. Our work reveals the superior catalytic performance of Pt/CNHs which may be a promising substitute for commercial Pt/C.

Facile preparation of Ni nanowire embedded nitrogen and sulfur dual-doped carbon nanofibers and its superior catalytic activity toward urea oxidation

A novel hairy-shaped Ni nanowire embedded nitrogen and sulfur dual-doped carbon nanofibers (Ni/N,S-CNFs) with superior electrocatalytic properties for urea oxidation reaction (UOR) was reported. The Ni/N,S-CNFs was prepared by electrospinning and carbonization process, using melamine-trithiocyanuric acid (MTCA) aggregates as both the N and S element sources. Noteworthy, MTCA also favored the formation of Ni nanowire via vapor liquid-solid mechanism, while Ni nanoparticles loaded CNFs (Ni/CNFs) was obtained without MTCA. For UOR tests, a high peak current intensity of 37.0 mA mg-1 was obtained on Ni/N,S-CNFs at 0.42 V (vs. SCE), 2-times higher of that on Ni/CNFs. Besides, the catalytic stability of Ni/N,S-CNFs was also improved. The enhanced catalytic properties of Ni/N,S-CNFs for UOR were ascribed to its unique Ni nanowires structure as well as the N, S dual-doping. Our work reveals that the property improvement of metal-based catalysts could be achieved by the heteroatom doping to fine the metal nanostructure.