An ultra-sensitive electrochemical immunosensor for detecting carcinoembryonic antigen was prepared. Graphene oxide-gold was used as the substrate modifier of the sandwich immunosensor. The high conductivity of graphene oxide effectively enhanced the electron transfer rate. The large specific surface area of graphene and the biocompatibility of gold nanoparticles increased the number of primary antibodies. The bovine serum albumin coated silver – platinum composite was used as a secondary antibody tag to prepare signal probes. The excellent biocompatibility of bovine serum albumin increased the number of secondary antibody connections. Silver nanoparticles increased the speed of electron transfer, and platinum further enhanced electrochemical sensing capabilities by catalyzing hydrogen peroxide. The immunosensor showed good performance for detecting carcinoembryonic antigen. Under the optimal conditions, the dynamic response range for carcinoembryonic antigen was from 0.005 ng·mL−1 to 100 ng·mL−1 with a detection limit of 0.76 pg·mL−1. The immunosensor also shown high selectivity, suitable stability, and good reproducibility, which provides new capabilities for clinical carcinoembryonic antigen detection.
As a novel material, metal-organic framework/graphite oxide (MIL-101(Cr)@GO) has great potential for the pretreatment of trace analytes. In the present study, MIL-101(Cr)@GO was synthesized using a solvothermal synthesis method at the nanoscale and was applied as sorbent in the dispersive micro-solid phase extraction (DMSPE) for the enrichment of the trace sulfonamides (SAs) from milk samples for the first time. Several experimental parameters including kinds of sorbents, the effect of pH, the amount of MIL-101(Cr)@GO, ionic strength , adsorption time, desorption solvent and desorption time were investigated. Under the optimal conditions, the linear ranges were from 0.1 to 10 μg/L, 0.2–20 μg/L or 0.5–50 μg/L for the analytes with regression coefficients ( r ) from 0.9942 to 0.9999. The limits of detection were between 0.012 and 0.145 μg/L. The recoveries ranged from 79.83% to 103.8% with relative standard deviations (RSDs)<10% ( n =3). MIL-101(Cr)@GO exhibited remarkable advantages compared to MIL-101(Cr), MIL-100(Fe), activated carbon and other sorbent materials used in pretreatment methods. A simple, rapid, sensitive, inexpensive and less solvent consuming method of DMSPE-ultra-high performance liquid chromatography-tandem mass spectrometry (DMSPE-UHPLC-MS/MS) was successfully applied to the pre-concentration and determination of twelve SAs in milk samples.
In this work, we have developed a novel method for preparing a CoOx/GO catalyst supported on ITO glass by electrochemical post-treatment of redox-active infinite coordination polymer (ICP) {Co(3,5-dbsq)(3,5-dbcat)(bix)} nanoparticles. Firstly, highly dispersed CoOx nanoparticles with ultra-small size and narrow size distribution (1.42 ± 0.34 nm) were in situ synthesized on ITO glass after electrochemical polarization of ICP coated on ITO glass at −1.1 V for 16.7 min (1000 s) in 0.10 mol L−1 KCl. Graphene oxide (GO) was next mixed with the ICP to obtain the CoOx/GO catalyst supported on ITO glass (the size of CoOx nanoparticles ranged within 1.21 ± 0.28 nm), which proved to have improved catalytic performance and enhanced stability compared to the pure CoOx. The catalytic activity of this CoOx/GO catalyst was then optimized according to the degradation efficiency of methylene blue (MB) via an advanced oxidation process in the presence of peroxymonosulfate (PMS). Under the optimal conditions here, the enhanced catalytic oxidative degradation of dye solution could be achieved easily. 100% of MB (2.0 mL, 20 mg L−1) could be decomposed within 6.7 min, which is better than other CoOx catalysts. With this kind of ITO glass as a component part, a portable reactor was constructed for the first time. Real-time monitoring of the catalytic degradation of colored wastewater from the textile and cosmetic industries was then achieved using this reactor directly by incorporating a UV/vis spectrometer, which is of great importance for information analysis and process control optimization during industrial wastewater treatment.
Palladium is an important metal as it has a wide range of applications in different fields but can cause cancer in human beings. Therefore, precise quantification of palladium is important. For this purpose, new material Ti 3 AlC 2 max phase having unique properties like high stability, thermal conductivity and environmental friendly has been synthesized. To increase its surface area of Ti 3 AlC 2 max phase, graphene oxide (GO) has been incorporated to form Ti 3 AlC 2 max phase GO nanocomposite. Ti 3 AlC 2 max phase GO nanocomposite was used as solid phase extracting material for microextraction and preconcentration of Pd(II) in environmental samples and medical appliances. Characterization of the adsorbent was achieved by using fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) and surface area analyzer (SAA). All the parameters that influence the extraction efficiency of the adsorbent like solution pH, amount of adsorbent, volume of sample, vortex time, desorption condition and interferences effect were determined and optimized. The limit of detection (0.327 µg/L) and limit of quantification (1.09 µg/L) show that the method is highly sensitive. The relative standard deviation was calculated as 5.48 % for five repeated measurements, which shows that the developed method is reproducible. The method is highly efficient with large values of preconcentration factor (20) and enhancement factors (20). The method was validated by applying the method to real water samples, soil samples and medical appliances with satisfied recovery results (94–106 %).
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