High-performance of plasma-enhanced Zn/MCM-41 catalyst for acetylene hydration

N,Zn-Doped Fluorescent Sensor Based on Carbon Dots for the Subnanomolar Detection of Soluble Cr(VI) Ions

The development of a fluorescent sensor has attracted much attention for the detection of various toxic pollutants in the environment. In this work, fluorescent carbon dots (N,Zn-CDs) doped with nitrogen and zinc were synthesized using citric acid monohydrate and 4-pyridinecarboxyaldehyde as carbon and nitrogen sources, respectively. The synthesized N,Zn-CDs served as an "off" fluorescence detector for the rapid and sensitive detection of hexavalent chromium ions (Cr(VI)). The zinc metal integrated into the heteroatomic fluorescent carbon dot played a functional role by creating a coordination site for the hydrogen ions that were displaced after the addition of Cr to the solution matrix. The stepwise addition of Cr(VI) effectively quenched the fluorescence intensity of the N,Zn-CDs, and this phenomenon was attributed to the internal filter effect. A low detection limit of 0.47 nmol/L for Cr(VI) was achieved in the fluorescence experiments. Real water samples were used to evaluate the practical application of N,Zn-CDs for the quantification of Cr(VI). The results show acceptable recoveries and agreement with ion chromatography-ultraviolet spectrometry results. These good recoveries indicate that the fluorescence probe is very well suited for environmental measurements.

Ultrasensitive fluorescence immunosensor based on mesoporous silica and magnetic nanoparticles: Capture and release strategy

Herein we designed a novel, highly sensitive, simple and amplified fluorescence immunosensing strategy for hepatitis B virus surface antigen (HBV surface antigen) (HBsAg) as a model based on the construction of a sandwich type probe. The operation mechanism of this immunosensing strategy is implemented by capturing and then stimulation-based-releasing of entrapped dye in the fluorescent capsules. The proposed probe is made by the Fe₃O₄ magnetic nanoparticle (Fe₃O₄ MNP) as a probe collector site and the Rhodamine B loaded-mesoporous silica nanoparticle (MSN-Rh.B) as a fluorescent mesoporous capsule and signal amplifier site. Such a methodology is benefited, from the advantages of the high ability of MSNs to be used as a scaffold for efficient dye encapsulation and the magnetic nanoparticles as efficient biological carriers. Under optimal conditions, the fluorescence signal (The fluorescence of solutions was measured using a quartz fluorescence cell (PMT voltage:720, Ex wavelegth:540, Em wavelength:568, All measurements were carried out at room temperature) increased with the increment of HBsAg concentration in the linear dynamic range of 6.1 ag/ml to 0.012 ng/ml with a detection limit (LOD) of 5.7 ag/ml. The relative standard deviation, measured between the resulting fluorescence peaks was obtained by 6.0%.