Polyoxometalate Functionalized Sensors: A Review

Abstract

Polyoxometalates (POMs) are a class of metal oxide complexes with a large structural diversity. Effective control of the final chemical and physical properties of POMs could be provided by fine-tuning chemical modifications, such as the inclusion of other metals or non-metal ions. In addition, the nature and type of the counterion can also impact POM properties, like solubility. Besides, POMs may combine with carbon materials as graphene oxide, reduced graphene oxide or carbon nanotubes to enhance electronic conductivity, with noble metal nanoparticles to increase catalytic and functional sites, be introduced into metal-organic frameworks to increase surface area and expose more active sites, and embedded into conducting polymers. The possibility to design POMs to match properties adequate for specific sensing applications turns them into highly desirable chemicals for sensor sensitive layers. This review intends to provide an overview of POM structures used in sensors (electrochemical, optical, and piezoelectric), highlighting their main functional features. Furthermore, this review aims to summarize the reported applications of POMs in sensors for detecting and determining analytes in different matrices, many of them with biochemical and clinical relevance, along with analytical figures of merit and main virtues and problems of such devices. Special emphasis is given to the stability of POMs sensitive layers, detection limits, selectivity, the pH working range and throughput.

Thermal Structure Transformation of Methylammonium Vanadate and it's Application as a Negative Staining Reagent for Observing SARS‐CoV‐2

“…[1] Polyoxometalates form a wide variety of compositions and structures that produce different physical and chemical properties, such as negative charges, oxo‐enriched surfaces, acid‐base properties, and redox potential. [ 1 , 2 , 3 ] These properties have led to their wide use as the main compounds in catalysts,[ 4 , 5 ] electrocatalysts,[ 6 , 7 ] medicines, [8] sensors, [9] and staining reagents. [ 10 , 11 ] Normally, polyoxometalates are synthesized via the condensation of oxoanions (MoO 4 2− , WO 4 2− , or VO 4 3− ) using a self‐assembly process.…”

Proton Affinity in the Chemistry of Beta-Octamolybdate: HPLC-ICP-AES, NMR and Structural Studies

“…However, several studies of polyoxomolybdates’ reactivity [ 39 ] and catalytic performance (electron transfer reactions) appeared [ 40 , 41 , 42 , 43 , 44 , 45 ]. One of the central complexes in this chemistry is (Bu 4 N) 4 [β-Mo 8 O 26 ] ( Scheme 1 ), which is a standard precursor of all reactions in organic media, leading to a huge number of materials with different properties [ 46 , 47 , 48 , 49 ]. Our ongoing research focuses on the use of the coordination chemistry of the [β-Mo 8 O 26 ] 4− anion in the study of silver chemistry in non-aqueous solutions [ 50 , 51 , 52 ].…”

Supramolecular Host–Guest Assembly Based on Phosphotungstate Nanostructures for Pseudocapacitive and Electrochemical Sensing Applications

“…On the other hand, electrochemical sensors have very strict requirements on electrode materials. Traditional electrochemical sensors are often classified into two types, with or without enzymes, depending on whether or not enzymes are involved. − Enzyme-based sensors modified by organic biological macromolecules often have complex preparation processes and short effective lifetimes and are easily affected by the environment. − In contrast, most enzyme-free sensing materials are directly composed of inorganic nanomaterials, such as metal oxides , and metal hydroxides. − The performance and stability of these materials can be improved by modulating their morphology, but the high efficiency and specificity of molecular recognition are often insufficient. Therefore, the development of electrode materials that can avoid these defects, without changing the detection performance of the sensor itself, is the key to fundamentally improve the performance of electrochemical sensors.…”