Synthesis and Applications of Prussian Blue and Its Analogues as Electrochemical Sensors

Gold brocade coated CoFe PBA with enhanced peroxidase-like activity for a chemiluminescent imaging immunoassay

Traditional chemiluminescence (CL) imaging immunoassays usually rely on natural enzymes as catalytic probes, which has hampered their extensive application due to the susceptibility to inactivation of natural enzymes. In response, a gold brocade coated CoFe Prussian blue analogue (CoFe PBA@Au brocade) with enhanced peroxidase-like activity was synthesized and utilized as a powerful label probe for constructing a highly sensitive CL imaging immunosensor targeting disease biomarkers with excellent performance. This research offers a universal strategy for enhancing the sensitivity of CL imaging immunoassays and further expands the application of PBA nanozymes.

From lab to field: Prussian blue frameworks as sustainable cathode materials

Prussian blue and Prussian blue analogues have attracted increasing attention as versatile framework materials with a wide range of applications in catalysis, energy conversion and storage, and biomedical and environmental fields. In terms of energy storage and conversion, Prussian blue-based materials have emerged as suitable candidates of growing interest for the fabrication of batteries and supercapacitors. Their outstanding electrochemical features such as fast charge-discharge rates, high capacity and prolonged cycling life make them favorable for energy storage application. Furthermore, Prussian blue and its analogues as rechargeable battery anodes can advance significantly by the precise control of their structure, morphology, and composition at the nanoscale. Their tunable structural and electronic properties enable the detection of many types of analytes with high sensitivity and specificity, and thus, they are ideal materials for the development of sensors for environmental detection, disease trend monitoring, and industrial safety. Additionally, Prussian blue-based catalysts display excellent photocatalytic performance for the degradation of pollutants and generation of hydrogen. Specifically, their excellent light capturing and charge separation capabilities make them stand out in photocatalytic processes, providing a sustainable option for environmental remediation and renewable energy production. Besides, Prussian blue coatings have been studied particularly for corrosion protection, forming stable and protective layers on metal surfaces, which extend the lifespan of infrastructural materials in harsh environments. Prussian blue and its analogues are highly valuable materials in healthcare fields such as imaging, drug delivery and theranostics because they are biocompatible and their further functionalization is possible. Overall, this review demonstrates that Prussian blue and related framework materials are versatile and capable of addressing many technical challenges in various fields ranging from power generation to healthcare and environmental management.

Prussian blue nanocubes with peroxidase-like activity for polyphenol detection in commercial beverages

The present study describes an efficient method for the determination of polyphenol content in beverages based on a composite material of graphene oxide decorated with Prussian blue nanocubes (rGO/PBNCs). In this method, rGO/PBNCs act as a nanoenzyme with peroxidase-like catalytic activity and produce a colorimetric product in the presence of hydrogen peroxide and tetramethylbenzidine (TMB). To verify the effectiveness of the method, we used two model standards for antioxidants: gallic acid (GA) and tannic acid (TA). The method validation included a comparison of the performance of a natural enzyme and an artificial one (rGO/PBNCs) and two polyphenols in the analysis of commercial beverage samples. After optimization, a pH of 4, ambient temperature (22 °C), a reaction time of 2 minutes and an rGO/PBNCs concentration of 0.01 μg mL-1 were found to be the most favorable conditions. The detection limits obtained were 5.6 μmol L-1 for GA and 1.5 μmol L-1 for TA. Overall, rGO/PBNCs offer advantages over natural enzymes in terms of stability, versatility, scalability and durability, making them attractive candidates for a wide range of catalytic and sensory applications.

Microstructure and Oxygen Evolution Property of Prussian Blue Analogs Prepared by Mechanical Grinding

Solvent-free mechanochemical synthesis of efficient and low-cost double perovskite (DP), like a cage of Prussian blue (PB) and PB analogs (PBAs), is a promising approach for different applications such as chemical sensing, energy storage, and conversion. Although the solvent-free mechanochemical grinding approach has been extensively used to create halide-based perovskites, no such reports have been made for cyanide-based double perovskites. Herein, an innovative solvent-free mechanochemical synthetic strategy is demonstrated for synthesizing Fe4[Fe(CN)6]3, Co3[Fe(CN)6]2, and Ni2[Fe(CN)6], where defect sites such as carbon-nitrogen vacancies are inherently introduced during the synthesis. Among all the synthesized PB analogs, the Ni analog manifests a considerable electrocatalytic oxygen evolution reaction (OER) with a low overpotential of 288 mV to obtain the current benchmark density of 20 mA cm-2. We hypothesize that incorporating defects, such as carbon-nitrogen vacancies, and synergistic effects contribute to high catalytic activity. Our findings pave the way for an easy and inexpensive large-scale production of earth-abundant non-toxic electrocatalysts with vacancy-mediated defects for oxygen evolution reaction.

UiO-66-Derived PBA Composite as Multifunctional Electrochemical Non-Enzymatic Sensor Realizing High-Performance Detection of Hydrogen Peroxide and Glucose

In this work, a highly efficient multifunctional non-enzymatic electrochemical sensor is successfully fabricated based on a facile two-step synthetic strategy. It resolves two important challenges of poor stability and low reproducibility compared to conventional electrochemical enzyme-based sensors. Herein, a metal-organic framework (UiO-66) is selected as a sacrificial template to construct the corresponding Prussian blue analogue (PBA) target to improve its stability and conductivity, namely, PBA/UiO-66/NF. Target PBA/UiO-66/NF exhibits excellent electrochemical sensing performance as hydrogen peroxide (H₂O₂) and glucose sensors with ultrahigh sensitivity of up to 1903 μA mM^-1 cm^-2 for H₂O₂ and 22,800 μA mM^-1 cm^-2 for glucose, as well as a very low detection limit of 0.02 μM (S/N = 3) for H₂O₂ and 0.28 μM for glucose. Especially, extremely high stability can be observed, which will be beneficial for practical application.

Ratiometric Electrochemical Sensor for Butralin Determination Using a Quinazoline-Engineered Prussian Blue Analogue

A ratiometric electrochemical sensor based on a carbon paste electrode modified with quinazoline-engineered ZnFe Prussian blue analogue (PBA-qnz) was developed for the determination of herbicide butralin. The PBA-qnz was synthesized by mixing an excess aqueous solution of zinc chloride with an aqueous solution of precursor sodium pentacyanido(quinazoline)ferrate. The PBA-qnz was characterized by spectroscopic and electrochemical techniques. The stable signal of PBA-qnz at +0.15 V vs. Ag/AgCl, referring to the reduction of iron ions, was used as an internal reference for the ratiometric sensor, which minimized deviations among multiple assays and improved the precision of the method. Furthermore, the PBA-qnz-based sensor provided higher current responses for butralin compared to the bare carbon paste electrode. The calibration plot for butralin was obtained by square wave voltammetry in the range of 0.5 to 30.0 µmol L^-1, with a limit of detection of 0.17 µmol L^-1. The ratiometric sensor showed excellent precision and accuracy and was applied to determine butralin in lettuce and potato samples.