The self‐assembly of sodium dodecyl benzene sulphonate (SDBS) functionalized graphene sheets (GSs) and horseradish peroxidase (HRP) by electrostatic attraction into novel hierarchical nanostructures in aqueous solution is reported. Data from scanning electron microscopy, high‐resolution transmission electron microscopy, and X‐ray diffraction demonstrate that the HRP–GSs bionanocomposites feature ordered hierarchical nanostructures with well‐dispersed HRP intercalated between the GSs. UV‐vis and infrared spectra indicate the native structure of HRP is maintained after the assembly, implying good biocompatibility of SDBS‐functionalized GSs. Furthermore, the HRP–GSs composites are utilized for the fabrication of enzyme electrodes (HRP–GSs electrodes). Electrochemical measurements reveal that the resulting HRP–GSs electrodes display high electrocatalytic activity to H2O2 with high sensitivity, wide linear range, low detection limit, and fast amperometric response. These desirable electrochemical performances are attributed to excellent biocompatibility and superb electron transport efficiency of GSs as well as high HRP loading and synergistic catalytic effect of the HRP–GSs bionanocomposites toward H2O2. As graphene can be readily non‐covalently functionalized by “designer” aromatic molecules with different electrostatic properties, the proposed self‐assembly strategy affords a facile and effective platform for the assembly of various biomolecules into hierarchically ordered bionanocomposites in biosensing and biocatalytic applications.
A facile and highly efficient magnetic solid-phase extraction method has been developed for Z-ligustilide, the major therapeutic agent in Angelica sinensis. The solid-phase adsorbent material used was prepared by conjugating carbon nanotubes with magnetic Fe3 O4 nanoparticles via a hydrothermal reaction. The magnetic material showed a high affinity toward Z-ligustilide due to the π-π stacking interaction between the carbon nanotubes and Z-ligustilide, allowing a quick and selective exaction of Z-ligustilide from complex sample matrices. Factors influencing the magnetic solid-phase extraction such as the amount of the added adsorbent, adsorption and desorption time, and desorption solvent, were investigated. Due to its high extraction efficiency, this method was proved highly useful for sample cleanup/enrichment in quantitative high-performance liquid chromatography analysis. The proposed method had a linear calibration curve (R(2) = 0.9983) over the concentration between 4 ng/mL and 200 μg/mL Z-ligustilide. The accuracy of the method was determined by the recovery, which was from 92.07 to 104.02%, with the relative standard deviations >4.51%.
Sum-frequency generation vibrational spectroscopy (SFG-VS) has been widely used for characterizing various interfaces. However, obtaining SFG signals with a high signal-to-noise ratio can be challenging for certain interfaces, such as those involving powder particles, which scatter the SFG light and make it difficult to obtain accurate spectra. To address these challenges, we developed a new approach using a z-cut α-quartz crystal as the substrate loaded with a very small amount of powder sample. This approach not only amplifies the SFG signal from particles through the interference of the electric field from the quartz crystal, but also allows for phase reference and normalization of the broadband infrared SFG spectrum. By distinguishing the different polarizations of the SFG light, we were able to separate and simultaneously collect the achiral and chiral SFG signals. We used the chiral SFG signal to normalize the achiral SFG intensity, thereby avoiding any potential changes to the interface caused by loading substances onto the quartz, as well as coincidence differences resulting from the instability of light at different moments. We demonstrated our method by measuring the adsorption of CH3OD on a quartz substrate loaded with MoC nanoparticles. Our approach produced a high signal-to-noise ratio SFG spectrum, regardless of the interface situation.
A simple and sensitive dopamine (DA) electrochemical sensor was fabricated based on magnetism-assisted modification of screen printed electrode (SPE) with magnetic multi-walled carbon nanotubes (mMWCNTs). The mMWCNTs modified electrodes (mMWCNTs/SPE) combines the advantages of SPE and the simultaneous contribution of magnetic nanoparticles (MNPs) and MWCNTs, increasing sensitivity and selectivity of DA detection. The linearity was found between 5μM to 180μM, with the limit of detection (LOD) of 0.43μM. In the mean time, this modified electrode exhibited excellent selectivity for DA detection with almost no interference from ascorbic acid (AA), which co-exists with DA in many bio-samples and causes common interference. Finally, this novel electrode has been applied to determine DA concentration in spiked human blood serum and satisfactory recovery was found in the range of 97.43-102.94% with the RSDs of less than 2.27%. This work developed a sensitive and reliable electrochemical analytical method based on mMWCNTs/SPE, which exhibits great potential for diagnosis of the diseases related to DA.
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