One-pot synthesis of hematite-alumina hollow sphere composite by ultrasonic spray pyrolysis technique with high adsorption capacity toward PAHs

Ionic liquids functionalized Fe3O4-based colorimetric biosensor for rapid determination of ochratoxin A

A stainless steel mesh (SSM) with the feature of flexibility was employed as the colorimetric biosensor substrate, and aptamer was bond onto the surface of the SSM. Through the cross-linking of ionic liquids (ILs), AuPt nanoparticles were deposited  onto the surface of Fe3O4 material to obtain a magnetic nanozyme with high peroxidase catalytic activity and rapid color change. Through the competing interaction of OTA and cDNA with aptamer, AuPt@IL@Fe3O4 signal probe was separated to catalyze the 3,3',5,5'-tetramethylbenzidine/hydrogen peroxide (TMB/H2O2) system to observe the color by bare eye and record the absorbance at 652 nm using a UV-spectrophotometer. Through the study of the catalytic properties on the basis of the Michaelis equation, AuPt@IL@Fe3O4 nanozyme presented a Vmax of 3.85 × 10-8 M s-1 and Km of 0.01 mM. Under the optimized conditions, the linear range of the colorimetric biosensor towards OTA was 5-100 ng mL-1, and the detection limit was 0.078 ng mL-1. This biosensor was applied to beer and corn samples with recoveries of 70.4-102.6% and 93.3-104.7%, respectively. Results showed that this sensor is a portable, rapid, economical, sensitive visual sensing platform towards mycotoxin in real samples.

Fabrication of MIL-101(Cr)/silver nanocomposites as SERS substrate for sensitive determination of malachite green and crystal violet in tilapia

Nanocomposites with multiple functions have attracted much attention in designing novel SERS substrates. In this report, the enrichment ability of MIL-101(Cr) and the local surface plasma resonance (LSPR) of silver nanoparticles are combined to fabricate a SERS substrate denoted as MIL-101-MA@Ag, which can simultaneously produce high-density and uniformly distributed hot spots. Moreover, the enrichment ability of MIL-101(Cr) can further improve the sensitivity by concentrating and transferring the analytes in the vicinity of hot spots. Under optimal conditions, MIL-101-MA@Ag showed good SERS activity for malachite green (MG) and crystal violet (CV), with detection limits as low as 9.5×10-11 M and 9.2×10-12 M at 1616 cm-1, respectively. The prepared substrate has been successfully applied to detect MG and CV in tilapia, the recovery rate of fish tissue extract was 86.4~102%, and the relative standard deviation (RSD) was 8.9~15%. The results demonstrate that MOF-based nanocomposites are expected to be useful SERS substrates and have a universal applicability for the detection of other hazardous molecules.

Facile synthesis of hollow spherical g-C3N4@LDH/NCQDs ternary nanostructure for multifunctional antibacterial and photodegradation activities

Heterojunction nanostructure construction and morphology engineering are considered to be effective approaches to improve photocatalytic performance. Herein, ternary hierarchical hollow structures consisting of cobalt-aluminum-layered double hydroxide (CoAl-LDH) nanoplates grown on hollow carbon nitride spheres (HCNS) and decorated with N-doped carbon quantum dots (NCQDs) were prepared using a templating method and a subsequent solvothermal process. The obtained HCNS@LDH/NCQD composites presented an improved performance in photocatalytic degradation of tetracycline and inactivation of E. coli compared with pure HCNS and LDH under visible light illumination. The enhanced photocatalytic activity of the designed photocatalyst could be attributed to the following reasons: (1) A special hollow structure provides more active sites and has multiple capabilities of light reflection by helping with a high specific surface area that improves the harvesting efficiency of solar light and (2) the strong synergistic effect among the constituents, which promotes separation and transfer of charge carriers and broadens the photo-response range.