Detection of Sudan I in Foods by a MOF‐5/MWCNT Modified Electrode

Synergistic enhancement of the Ag/ZIF-67 cage@MXene 3D heterogeneous structure for ultrahigh SERS sensitivity and stability

There is an urgent need in the in situ field for rapid extraction and analysis of target molecules from irregular surfaces. The application of SERS technology is often limited by low adhesion between precious metal nanoparticles and the substrate and complex fabrication processes. In order to solve this problem, a carbon fiber cloth (CFC) loaded Ag/ZIF-67 cage@MXene 3D detection platform (AZMC) was constructed in this study. The platform takes advantage of the large surface area and defects of MXene flakes to host noble metals, the high carrier transport efficiency between flakes, and van der Waals forces to build highly sensitive and stable composite SERS substrates. The hydrophilicity and subsurface oxidation behavior of MXene make its optoelectronic performance unstable. In this study, the ZIF-67 cage was chemically bonded to MXene through the Co-O-Ti bond, and the ZIF 67@MXene heterojunction was successfully constructed to maintain the optimal photoelectric stability and excellence of MXene. The high performance of the substrate stems from the synergistic effects of charge transfer (CT) and surface plasmon resonance (SPR) of AgNPs and MXene flakes, while the 3D nanocage structure provides additional hotspot regions. Substrate sensitivity was analyzed using rhodamine 6G (R6G) as a probe molecule (detection limit as low as 10-11 M). Notably, the AZMC substrate is highly stable (SERS performance remains essentially unchanged after 45 days of exposure to air). Using this substrate, we also successfully analyzed methylene blue (MB) molecules and Sudan I molecules on apple epidermis, which were successfully detected at concentrations of 0.5 mg L-1 and 1 mg L-1, respectively.

A Dual-Functional and Efficient MOF-5@MWCNTs Electrochemical Sensing Device for the Measurement of Trace-Level Acetaminophenol and Dopamine

The design and construction of dual-functional and high-efficiency electrochemical sensors are necessary for quantitative detection. In this work, a zinc-based metal-organic framework (MOF-5) and multi-walled carbon nanotubes (MWCNTs) were combined in situ through a simple solvothermal reaction to obtain an MOF-5@MWCNTs composite. The composite exhibits a large surface area, hierarchical pore structure, excellent conductivity, and enhanced electrochemical performance in the detection of acetaminophenol (AP) and dopamine (DA). Remarkably, the synergistic effects between MOF-5 and MWCNTs enable the electrochemical sensor based on the MOF-5@MWCNTs composite to quantitatively determine AP and DA at trace levels. Under optimal conditions, the proposed sensor features relatively wide linear ranges of 0.005-600 μM and 0.1-60 μM for AP and DA, respectively, with very low detection limits (LODs) of 0.061 μM and 0.0075 μM for AP and DA. Importantly, this electrochemical sensor demonstrates excellent reproducibility, stability, and anti-interference ability, making it suitable for practical applications in the detection of AP and DA in urine and tap water samples with acceptable recoveries. The successful integration of MOF-5 with MWCNTs results in a robust and versatile electrochemical sensing platform for the rapid and reliable detection of AP and DA at trace levels.

Metal-organic frameworks (MOFs) based luminescent and electrochemical sensors for food contaminant detection

With the increasing population, food toxicity has become a prevalent concern due to the growing contaminants of food products. Therefore, the need for new materials for toxicant detection and food quality monitoring will always be in demand. Metal-organic frameworks (MOFs) based on luminescence and electrochemical sensors with tunable porosity and active surface area are promising materials for food contaminants monitoring. This review summarizes and studies the most recent progress on MOF sensors for detecting food contaminants such as pesticides, antibiotics, toxins, biomolecules, and ionic species. First, with the introduction of MOFs, food contaminants and materials for toxicants detection are discussed. Then the insights into the MOFs as emerging materials for sensing applications with luminescent and electrochemical properties, signal changes, and sensing mechanisms are discussed. Next, recent advances in luminescent and electrochemical MOFs food sensors and their sensitivity, selectivity, and capacities for common food toxicants are summarized. Further, the challenges and outlooks are discussed for providing a new pathway for MOF food contaminant detection tools. Overall, a timely source of information on advanced MOF materials provides materials for next-generation food sensors.

Rapid quantitative detection of luteolin using an electrochemical sensor based on electrospinning of carbon nanofibers doped with single-walled carbon nanoangles

In this study, single-walled carbon nanoangles/carbon nanofibers (SWCNHs/CNFs) were synthesized by electrospinning, followed by annealing in a N₂ atmosphere. The synthesized composite was structurally characterized by scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The electrochemical sensor was fabricated by modifying a glassy carbon electrode (GCE) for luteolin detection, and its electrochemical characteristics were investigated using differential pulse voltammetry, cyclic voltammetry, and chronocoulometry. Under optimized conditions, the response range of the electrochemical sensor to luteolin was 0.01-50 μM, and the detection limit was 3.714 nM (S/N = 3). The SWCNHs/CNFs/GCE sensor showed excellent selectivity, repeatability, and reproducibility, thus enabling the development of an economical and practical electrochemical method for the detection of luteolin.

Sensing of azo toxic dyes using nanomaterials and its health effects - A review

Development of science has taken over our lives and made it mandatory to live with science. Synthetic technology takes more than it has given for our welfare. In the process of meeting the demand of the consumers, industries supported synthetic products to meet the same. One such sector that employs synthetic azo dyes for food coloring is the food industry. The result of the process is the production of a variety of colored foods which looks more appealing and palatable. The process not only meets the consumer's demand it also has an impact on customers' health because the consumption of azo-toxic dye-treated foods regularly or in direct contact with synthetic azo dyes can also cause severe human health consequences. Nanotechnology is a rapidly evolving branch of research in which nanosensors are being developed for a variety of applications, including sensing various azo-toxic dyes in food products, which provides a wider scope in the future, with the innovation in designing different nanosensors. The current review focuses on the different types of nanosensors, their key role in sensing, and the sensing of azo toxic dyes using nanosensors, their advantages over other sensors, applications of nanomaterials, and the health impacts of azo dyes on humans, appropriate parameters for maximum permissible limits, and an Acceptable Daily Intake (ADI) of azo toxic dye to be followed. The regulations followed on the application of colorants to the food are also elaborated. The review also focuses on the application of enzyme-based biosensors in detecting azo dyes in food products.

Potentiometric MIP-Modified Screen-Printed Cell for Phenoxy Herbicides Detection

In this study, a molecularly imprinted polymer (MIP)-based screen-printed cell is developed for detecting phenoxy herbicides using 2-methyl-4-chlorophenoxyacetic acid (MCPA) as the template. MCPA is a phenoxy herbicide widely used since 1945 to control broadleaf weeds via growth regulation, primarily in pasture and cereal crops. The potentiometric cell consists of a silver/silver chloride pseudo-reference electrode and a graphite working electrode coated with a MIP film. The polymeric layer is thermally formed after drop-coating of a pre-polymeric mixture composed of the reagents at the following molar ratio: 1 MCPA: 15 MAA (methacrylic acid): 7 EGDMA (ethylene glycol dimethacrylate). After template removal, the recognition cavities function as the ionophore of a classical ion selective electrode (ISE) membrane. The detected ion is the deprotonated MCPA specie, negatively charged, so the measurements were performed in phosphate buffer at pH 5.5. A linear decrease of the potential with MCPA concentration, ranging from 4 × 10-8 to 1 × 10-6 mol L-1, was obtained. The detection limit and the limit of quantification were, respectively, 10 nmol L-1 and 40 nmol L-1. A Nernstian slope of about -59 mV/dec was achieved. The method has precision and LOD required for MCPA determination in contaminated environmental samples.

Electrochemical detection of Sudan red series azo dyes: Bibliometrics based analysis

Sudan red azo dyes are banned from food because of their carcinogenic properties. It is necessary to establish a method for the detection of Sudan azo dyes in food. Among them, electrochemical sensing technology has become a very potential analytical method for food detection because of its fast, sensitive and low price. In this paper, we analyze the electrochemical detection of Sudan red azo dyes by bibliometric method. A total of 161 articles were analyzed from 2007 to 2021. The geographical and institutional distribution of these papers is used to understand the form of collaboration on this topic. Keyword analysis in these papers is used to understand the different directions in which the topic is studied at different stages. The results show that the topic reached its peak in 2015. The development of novel materials with excellent electrochemical activity has promoted the research on this topic. As detection limits continue to be lowered and sensors continue to be optimized, this topic currently does not continue to attract much attention.

Fabrication of hierarchical Ru/PEDOT:PSS/Ti3C2Tx nanocomposites as electrochemical sensing platforms for highly sensitive Sudan I detection in food

In our paper, a promising electrochemical sensing platform was fabricated with titanium carbide (Ti₃C₂T_x), poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), and ruthenium nanoparticles (RuNPs). First, the Shandong pancake structural PEDOT:PSS/Ti₃C₂T_x was prepared by physical stirring. PEDOT:PSS as the dispersant was embedded into the Ti₃C₂T_x nanosheets, increasing the degree of dispersion of the Ti₃C₂T_x nanosheets and further improving the specific surface area of the composite material. Then, RuNPs were supported on the surface of PEDOT:PSS/Ti₃C₂T_x to form the hierarchical ternary nanocomposite of Ru/PEDOT:PSS/Ti₃C₂T_x. The prepared Ru/PEDOT:PSS/Ti₃C₂T_x nanocomposite exhibited promising electrochemical sensing properties toward Sudan I detection with a wide detection range of 0.01 ∼ 100 μM and a high sensitivity of 482.43 μA mM^-1 cm^-2. Moreover, the Ru/PEDOT:PSS/Ti₃C₂T_x sensing platform has been successfully applied for Sudan I detection in ketchup and chili paste, implying the promising application prospect of Ru/PEDOT:PSS/Ti₃C₂T_x in food safety testing.

An electrochemical method for the sensitive and rapid sensing of Sudan I in food based on Ni–Fe bimetal organic frameworks

A Ni–Fe bimetal organic framework-modified electrode was constructed for the sensitive and rapid sensing of Sudan I in food.