Rutin, a natural flavonol glycoside, is widely present in plants and foods, such as black tea and wheat tea. The antioxidant and anti-inflammatory effects of flavonoids are well known. In this study, a new electrochemical rutin sensor was developed using multiwalled carbon nanotubes/aluminum-based metal–organic frameworks (MWCNT/CAU-1) (CAU−1, a type of Al-MOF) as the electrode modification material. The suspension of multiwalled carbon tubes was dropped on the surface of the GCE electrode to make MWCNT/GCEs, and CAU−1 was then attached to the electrode surface by electrodeposition. MWCNTs and CAU−1 were characterized using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Due to the synergistic effect of CAU−1 and MWCNT-COOH, the prepared sensor showed an ultrasensitive electrochemical response to rutin. Under optimized conditions, the sensor showed a linear relationship between 1.0 × 10−9~3.0 × 10−6 M with a detection limit of 6.7 × 10−10 M (S/N = 3). The sensor also showed satisfactory stability and accuracy in the detection of real samples.
Catechin (Cat) is one of the primary functional components of tea, and its accurate detection is significant for understanding the health benefits of tea. In this study, cyclodextrin nanosponges (CDNS) were prepared and employed to combine with graphene quantum dots (GQDs) and carboxylated multi‐walled carbon nanotubes (MWCNTs‐COOH) to form a CDNS/GQDs/MWCNTs‐COOH composite. Scanning electron microscope and X‐ray diffraction were used to characterize the composite which was used to build a new electrochemical Cat sensor. The abundance of cavities, intermolecular gaps, and surface active groups of CD molecules endowed CDNS with remarkable Cat enrichment capacity. Due to the outstanding biocompatibility of GQDs, the good electrocatalytic activity of MWCNTs‐COOH, and the enrichment capacity of CDNS, the composite modified glass carbon electrode (GCE) exhibited excellent electrochemical sensing performance. The CDNS/GQDs/MWCNTs‐COOH/GCE showed a sensitive peak current response to catechins in the linear range between 2 × 10−8 and 1.2 × 10−6 M, with a minimum limit of detection (S/N = 3) of 4.45 nM. The sensor has also been successfully applied for catechin detection in tea beverages.
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