A comprehensive review of the application of Zr-based metal-organic frameworks for electrochemical sensors and biosensors.

A family of inorganic-organic hybrid crystalline materials made up of organic ligands and metal cations or clusters is known as metal-organic frameworks (MOFs). Because of their unique stability, intriguing characteristics, and structural diversity, zirconium-based MOFs (Zr-MOFs) are regarded as one of the most interesting families of MOF materials for real-world applications. Zr-MOFs that have the ligands, metal nodes, and guest molecules enclosed show distinct electrochemical reactions. They can successfully and sensitively identify a wide range of substances, which is important for both environmental preservation and human health. The rational design and synthesis of Zr-MOF electrochemical sensors and biosensors, as well as their applications in the detection of drugs, biomarkers, pesticides, food additives, hydrogen peroxide, and other materials, are the main topics of this comprehensive review. We also touch on the current issues and potential future paths for Zr-MOF electrochemical sensor research.

A comprehensive review on electrochemical and optical aptasensors for organophosphorus pesticides.

There has been a rise in pesticide use as a result of the growing industrialization of agriculture. Organophosphorus pesticides have been widely applied as agricultural and domestic pest control agents for nearly five decades, and they remain as health and environmental hazards in water supplies, vegetables, fruits, and processed foods causing serious foodborne illness. Thus, the rapid and reliable detection of these harmful organophosphorus toxins with excellent sensitivity and selectivity is of utmost importance. Aptasensors are biosensors based on aptamers, which exhibit exceptional recognition capability for a variety of targets. Aptasensors offer numerous advantages over conventional approaches, including increased sensitivity, selectivity, design flexibility, and cost-effectiveness. As a result, interest in developing aptasensors continues to expand. This paper discusses the historical and modern advancements of aptasensors through the use of nanotechnology to enhance the signal, resulting in high sensitivity and detection accuracy. More importantly, this review summarizes the principles and strategies underlying different organophosphorus aptasensors, including electrochemical, electrochemiluminescent, fluorescent, and colorimetric ones.

Electrochemical sensor based on glassy carbon electrode modified by polymelamine formaldehyde/graphene oxide nanocomposite for ultrasensitive detection of oxycodone.

Polymelamine formaldehyde/graphene oxide (PMF/GO) nanocomposite was used, for the first time, to study the ultrasensitive and selective electrochemical detection of oxycodone (OXC). The successful characterization of PMF/GO was verified based on scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and Raman spectroscopy. The modified GCE (PMF/GO-GCE) proved its electrocatalytic effect on OXC determination according to cyclic, linear sweep, and differential pulse voltammetry (CV, LSV, and DPV) and electrochemical impedance spectroscopy (EIS) studies. The developed sensor under optimal conditions offered a linear relationship in a limited range of  0.01 to 45 µmol L-1 with the limit of detection (LOD) of 2.0 nmol L-1. The proposed PMF/GO-GCE sensor was effectively employed for the OXC detection in human urine and serum samples. Graphical abstract.

Ultrasensitive voltammetric and impedimetric aptasensor for diazinon pesticide detection by VS2 quantum dots-graphene nanoplatelets/carboxylated multiwalled carbon nanotubes as a new group nanocomposite for signal enrichment.

Polluted water and groundwater resources contaminated by pesticides are among the most important environmental distresses. Therefore, a simple, ultrasensitive, and selective electrochemical aptasensor is proposed for diazinon (DZN) determination as an organophosphorus compound. The vanadium disulfide quantum dots (VS2QDs) were synthesized by a facile hydrothermal method and doped on the graphene nanoplatelets/carboxylated multiwalled carbon nanotubes (GNP/CMWCNTs) as a new group of nanocomposite. The prepared nanocomposite (VS2QDs-GNP/CMWCNTs) on a glassy carbon electrode (GCE) was incubated with the DZN binding aptamer (DZBA) through electrostatic interaction (GCE/VS2QDs-GNP/CMWCNTs/DZBA). The modified electrode was used for the low detection of DZN by monitoring the oxidation of [Fe(CN)6]3-/4- as the redox probe. The characterizations of the modified electrode were performed by several electrochemical methods include: cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). Also, the prepared nanocomposite was characterized with field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), UV-Vis absorption spectroscopy, fourier transform infrared (FT-IR), fluorescence emission spectroscopy, dynamic light scattering (DLS), elemental mapping, and energy dispersive spectroscopy (EDS). The DZBA selectively adsorbs DZN on the modified electrode, leading to a decrease and increase in the current of DPV and charge transfer resistance (RCT) of EIS, respectively, as analytical signals. The developed electrochemical aptasensor at the optimal conditions have low limits of detection (LOD) equal to 1.1 × 10-14 and 2.0 × 10-15 mol L-1 with wide dynamic ranges of 5.0 × 10-14-1.0 × 10-8 mol L-1 and 1.0 × 10-14-1.0 × 10-8 mol L-1 for DPV and EIS calibration curves, respectively. Finally, this aptasensor had good selectivity, stability, reproducibility, and feasibility for the DZN detection in various real samples.