Organic–Inorganic Hybrid Cerium-Encapsulated Selenotungstate Including Three Building Blocks and Its Electrochemical Detection of Dopamine and Paracetamol

The Assembly of Cerium(III)-Containing Silicotungstate with Lewis Acid-Base Sites Enables the Selective C3-Alkenylation of Oxindole

A cerium(III)-containing silicotungstate, [H2N(CH3)2]10NaK[KCe(SiW11O39)2(H2O)]·18.5H2O (CeSiW), was successfully synthesized and characterized. Structure analysis reveals that CeSiW is composed of two {SiW11O39} units connected by one cerium(III) cation to form a typical 1:2 sandwich structure, which is further expanding into a 1D chain linked by K+ ions. The oxygen-enriched surfaces of {SiW11O39} units and open cerium sites provide abundant Lewis base and acid sites in CeSiW. As a result, CeSiW efficiently catalyzed the C3-alkenylation of oxindoles with aldehydes through the simultaneous activation of both reaction substrates on its crystal framework. Various 3-benzylidene-oxindoles are synthesized with excellent yields and high E-selectivity under solvent-free conditions.

Dy/Ho-encapsulated tartaric acid-functionalized tungstoantimonates: heterogeneous catalysts for isoindolinone synthesis

Two novel rare earth-substituted tungstoantimonates [H2N(CH3)2]8Na12[Dy2(H2O)6(tar)(Sb2W21O72)]2·40H2O (DySbW) and [H2N(CH3)2]6Na14[Ho2(H2O)6(tar)(Sb2W21O72)]2·25H2O (HoSbW) (H4tar = tartaric acid) were synthesized. The meso-polyanions are alternately linked by {Na3(H2O)3} clusters and DL-tar ligands to form 1D chains. Notably, HoSbW exhibits excellent catalytic activity and high stability for the synthesis of isoindolinones using EtOH as a green solvent.

Advances in polyoxometalate-based electrochemical sensors in the last three years

As a famous subclass of metal-oxide cluster materials, polyoxometalates (POMs) feature variable architectures, reversible multi-electron transport capability, catalytic activity, and redox capacity. These attributes endow POMs with great potential as promising electrode materials in electrochemical sensors (ECSs). Up to now, POM-based ECSs have been passionately studied, and diverse POM-based redox ECSs, aptasensors and immunosensors have emerged. And these POM-based ECSs generally demonstrate fast response, low detection limit, strong selectivity and high antijamming capability. This review mainly focuses on the remarkable advancement of POM-based ECSs in environmental monitoring, food safety and biomedicine from 2021, aiming to furnish theoretical insights that inform the design and development of innovative sensors.

Recent research progress of selenotungstate-based biomolecular sensing materials

Polyoxometalates (POMs) have drawn significant attention on account of their structural designability, compositional diversity and great potential applications. As an indispensable branch of POMs, selenotungstates (SeTs) have been synthesized extensively. Some SeTs have been applied as sensing materials for detecting biomarkers (e.g., metabolites, hormones, cancer markers). To gain a comprehensive understanding of advancements in SeT-based sensing materials, we present an overview that encapsulates the sensing performances and mechanisms of SeT-based biosensors. SeT-based biosensors are categorized into electrochemical catalytic biosensors, electrochemical affinity biosensors, "turn-off" fluorescence biosensors and "turn-on" fluorescence biosensors. We anticipate the expansive potential of SeT-based biosensors in wearable and implantable sensing technologies, which promises to catalyze significant breakthroughs in SeT-based biosensors.

2,5-Thiophenedicarboxylic Acid Bridging Hexameric CeIII-Substituted Selenotungstate and Its Application for Detecting Mucin 1

The development of polyoxometalate chemistry not only is derived from the continuous discovery of novel polyoxometalates (POMs) but also stems from the exploitation of their new functionalities. In this work, we obtained a rigid sulfur-containing heterocyclic ligand-linking aggregate [N(CH3)4]10Na6H6[Ce8(H2O)26W8(HTDA)2(TDA)2O20][SeW4O18]2[SeW9O33]4·112H2O (1) (H2TDA = 2,5-thiophenedicarboxylic acid). Its polyanionic unit consists of one [Ce4(H2O)13W4O10(HTDA)(TDA)O10]18+ cluster and two kinds of Keggin-type [SeW4O18] and [SeW9O33] segments. It is noteworthy that H2TDA ligands not only work as connectors to link two symmetrical {[Ce4(H2O)13W4(HTDA)(TDA)O10][SeW4O18][SeW9O33]2}11- units but also function as ornaments to graft to the polyanionic backbone. Furthermore, 1 and 3,4-ethylenedioxythiophene (EDOT) were deposited on the glassy carbon electrode (GCE) by the electropolymerization (EPM) method, resulting in a 1-poly(3,4-ethylenedioxythiophene) (1-PEDOT) composite film, which can provide sufficient binding sites to immobilize Au nanoparticles (Au NPs). Hereafter, the Au NPs-immobilized 1-PEDOT modified electrode (Au/1-PEDOT/GCE) was used to construct an electrochemical aptasensor to detect mucin 1, showing a low detection limit of 29.5 fM in the Tris solution. This work not only demonstrates that rigid heterocyclic ligands are beneficial for the creation of novel rare-earth-substituted selenotungstate hybrids but also provides more enlightenment for POM-based materials used for electrochemical detection of cancer markers.

Two Tetra-Nuclear Ln-Substituted Prazine Dicarboxylic Acid-Functionalized Selenotungstates with Catalytic Oxidation of Thioether Properties

Two two-dimensional Ln-substituted prazine dicarboxylic acid-functionalized selenotungstates Na3H9[(H2N(CH3)2]2{(Se4W27O100)[Ln4(H2O)8(Hpzdc)2(pzdc)]}·26H2O [Ln = Nd (1) and Ce (2)]; H2pzdc = 2,3-pyrazine dicarboxylic acid) have been synthesized by one-pot self-assembly strategy, in which the basic polyanion [Se4W27O100]22-was composed of two [SeW8O31]10- fragments, a [SeW9O33]8- segment and an intriguing {SeO} group, simultaneously tetra-nuclear Ln3+ ions with H2pzdc pendants were embedded. Compounds 1 and 2 showed excellent catalytic oxidation of thioether properties within a short time (20 min) with high 100% conversion and 98.9% selectivity. In addition, the pioneering Ln-substituted selenotungstates were used as catalysts to degrade sulfur mustard simulant 2-chloroethyl ethyl sulfide at room temperature with 99% conversion and 100% selectivity. The chemical kinetic experiment studies revealed that the catalytic reaction was in compliance with the first-order reaction, and the kinetic half-life (t1/2) values were 3.814 and 3.849 min, respectively.

Heteroatom-Modulated Assembly of Hexalanthanoid-Containing Polyoxometalate-Based Coordination Networks

Two series of lanthanoid (Ln)-containing polyoxometalates (POMs) {[Ln₆(ampH)₄(H₂O)_24-n(ampH₂)_n(PW₁₁O₃₉)₂]·21H₂O (Ln = Tb, n = 0 (1), Ln = Er, n = 1 (2)) and K₂[Ln₆(ampH)₄(H₂O)₂₂(SiW₁₁O₃₉)₂]·23H₂O (Ln = Tb (3), Er (4)) (ampH₂ = (aminomethyl) phosphonic acid)} have been synthesized with tri-lacunary Keggin-type POMs containing different types of heteroatoms. Compounds 1 and 2 display neutral organic-inorganic hybrid POM molecules containing {Ln₆(ampH)₄} ({Ln₆}) cores sandwiched by two {PW₁₁O₃₉} units. By changing the heteroatoms from P^V to Si^IV, the extended 2D networks of 3 and 4 were successfully isolated where the adjacent {Ln₆} clusters were connected by {SiW₁₁O₃₉} moieties. Luminescence performances and magnetic properties of 1-4 have been systematically surveyed. The solid-state fluorescence spectra of 1-4 display characteristic emissions of Ln components resulting from the 4f-4f transitions, and energy transfer from the POM segments to Ln³⁺ centers in 1 and 3 has been observed based on the lifetime decay behaviors. Furthermore, all compounds can be utilized as electrocatalysts toward reduction of nitrite with high stability.

A bibliometric analysis of graphene in acetaminophen detection: Current status, development, and future directions

Acetaminophen is a widely used analgesic throughout the world. Detection of acetaminophen has particular value in pharmacy and clinics. Electrochemical sensors assembled with advanced materials are an effective method for the rapid detection of acetaminophen. Graphene-based carbon nanomaterials have been extensively investigated for potential analytical applications in the last decade. In this article, we selected papers containing both graphene and acetaminophen. Bibliometrics was used to analyze the relationships and trends among these papers. The results show that the topic has grown at a high rate since 2009. Among them, the detection of acetaminophen by an electrochemical sensor based on graphene is the most important direction. Graphene has moved from being a primary sensing material to a substrate for immobilization of other active ingredients. In addition, the degradation of acetaminophen using graphene-modified electrodes is also an important direction. We analyzed the research history and current status of this topic through bibliometrics. Authors, institutions, countries, and key literature were discussed. We also proposed perspectives for this topic.

Two Innovative Fumaric Acid Bridging Lanthanide-Encapsulated Hexameric Selenotungstates Containing Mixed Building Units and Electrochemical Performance for Detecting Mycotoxin

Two particular fumaric acid bridging lanthanide-encapsulated selenotungstates [H₂N(CH₃)₂]₁₆Na₈[Ln₃(H₂O)₇]₂ [W₄O₈(C₄H₂O₄) (C₄H₃O₄)]₂[SeW₆O₂₅]₂[B-α-SeW₉O₃₃]₄·46H₂O [Ln = Ce³⁺ (1), La³⁺ (2)] were acquired by the deliberately designed step-by-step synthetic strategy, which are composed of four trilacunary Keggin [B-α-SeW₉O₃₃]^8- and two original [SeW₆O₂₅]^10- building units together with one fumaric acid bridging heterometallic [Ln₃(H₂O)₇]₂[W₄O₈(C₄H₂O₄) (C₄H₃O₄)]₂²⁸⁺ entity. Particularly, this heterometallic cluster contains four fumaric acid ligands, which play two different roles: one works as the pendant decorating the cluster and the other acts as the linker connecting the whole structure. In addition, the 1@DDA hybrid material was produced through the cation exchange of 1 and dimethyl distearylammonium chloride (DDA·Cl) and its beehive-shaped film of 1@DDA was prepared by the breath figure method, which can be further used to establish an electrochemical biosensor for detecting a kind of mycotoxin-ochratoxin A (OX-A). The 1@DDA beehive-shaped film-based electrochemical biosensor exhibits good reproducibility and specific sensing toward OX-A with a low detection limit of 29.26 pM. These results highlight the huge feasibility of long-chain flexible ligands in building lanthanide-encapsulated selenotungstates with structural complexity and further demonstrate great electrochemical application potentiality of polyoxometalate-involved materials in bioanalysis, tumor diagnosis, and iatrology.

The largest Se-4f cluster incorporated polyoxometalate with high Lewis acid-base catalytic activity

A 4p-4f cluster incorporated polyoxometalate (POM), namely, H₁₈{[(H₄pic)₄Eu₁₀Se₁₃O₂₈(H₂O)₁₂](α-GeW₉O₃₄)₄·40H₂O (1-Eu, H₄pic = isonicotinic acid), has been first synthesized and characterized. 1-Eu features an interesting four-shell structure, representing the largest Se-4f cluster incorporated POM known to date. Besides, 1-Eu exhibits excellent Lewis acid-base catalytic activity and reusablity in catalyzing the gram-scale dehydration condensation reaction of hydrazines and 1,3-diketones to synthesize polysubstituted pyrazoles.

Polyoxometalate Functionalized Sensors: A Review

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.

Fluorometric and colorimetric detection of cerium(IV) ion using carbon dots and bathophenanthroline-disulfonate-ferrum(II) complex

Cerium, an abundant lanthanide element, is widely used in human industry. The accumulation of Ce⁴⁺ ion, however, will damage the environment and biological organism. Therefore, its facile detection is highly needed. Herein, we design a hybrid sensing platform consisting of carbon dots (C-dots) and bathophenanthroline-disulfonate-Fe²⁺ complex (Bphen-Fe²⁺) for trace-level determination of Ce⁴⁺. Based on inner filter effect (IFE), the red-colored Bphen-Fe²⁺ complex severely quenches the fluorescence of C-dots. After addition of Ce⁴⁺, Fe²⁺ is oxidized to Fe³⁺, and the colorless Bphen-Fe³⁺ complex generates, which weakens the IFE efficiency and leads to the fluorescence recovery of C-dots. Meanwhile, due to the decreasing amount of Bphen-Fe²⁺ upon Ce⁴⁺ addition, the red color of the solution gradually fades, which enables visual detection of Ce⁴⁺ by the naked eyes. Under the optimized conditions, the C-dots/Bphen-Fe²⁺ system realizes the fluorometric and colorimetric sensing of Ce⁴⁺ in the range of 0.5-100 and 1.9-80 μM, with the limits of detection as low as 0.5 and 1.9 μM, respectively. This method also shows high selectivity over other common ions, and has an excellent applicability for monitoring of Ce⁴⁺ in real water samples.

Dual-heteroatom-templated lanthanoid-inserted heteropolyoxotungstates simultaneously comprising Dawson and Keggin subunits and their composite film applied for electrochemical immunosensing of auximone

Two unprecedented PIII–SbIII-heteroatom templated lanthanide-inserted heteropolyoxotungstates were obtained and their composite film was applied for the electrochemical immunosensing of auximone.

Organic–inorganic hybrid phosphite-participating S-shaped penta-CeIII incorporated tellurotungstate as electrochemical enzymatic hydrogen peroxide for β-D-glucose detection

Polyoxometalate chemistry has made rapid advances in innovative structural chemistry. The lower valence state and lone electron pair effect of subgroup-valence heteroatom Te(IV) can be introduced into the tungsten-oxygen system...

A {Ti6W4}-Cluster-Substituted Polyoxotungstate: Synthesis, Structure, and Catalytic Oxidation Properties

A novel Ti-W-O-cluster-substituted tungstoantimonate (TA), [H₂N(CH₃)₂]₃Na₄H₉[{Ti₆W₄O₁₈(OH)(H₂O)₃}(B-α-SbW₉O₃₃)₃]·20H₂O (1), has been made by hydrothermal reactions of trivacant [B-α-SbW₉O₃₃]^9- units, Ti⁴⁺ cations, and WO₄^2- anions in the presence of [H₂N(CH₃)₂]·Cl and structurally characterized. Intriguingly, the polyoxoanion of 1 is constructed from three [B-α-SbW₉O₃₃]^9- units and a previously unobserved decanuclear heterometallic Ti-W-O cluster [Ti₆W₄O₁₈(OH)(H₂O)₃]¹¹⁺ ({Ti₆W₄}) that is comprised of an octahedral [Ti₆WO₆(H₂O)₃]¹⁸⁺ cluster and an edge-sharing [W₃O₁₂(OH)]^7- fragment via six W-O-Ti/W linkers. Furthermore, studies on the catalytic oxidation properties reveal that 1 possesses good catalytic activity toward the oxidation reactions of various sulfides and cyclooctene based on the environmentally friendly oxidant H₂O₂.

Nicotinic-Acid-Ornamented Tetrameric Rare-Earth-Substituted Phospho(III)tungstates with the Coexistence of Mixed Keggin/Dawson Building Blocks and Its Honeycomb Nanofilm for Detecting Toxins

A fascinating class of nicotinic-acid-ornamented tetrameric rare-earth (RE)-substituted phospho(III)tungstates [NH₂(CH₃)₂]₁₀Na₄H₈[RE₂(NA)(HNA)(H₂O)₆(W₂O₄)(β-H₂P₂^IIIW₁₃O₄₉)(α-HP^IIIW₉O₃₃)]₂·22 H₂O [RE = Nd³⁺ (1-Nd), Tb³⁺ (2-Tb), Dy³⁺ (3-Dy), Ho³⁺ (4-Ho), HNA = nicotinic acid] were isolated through a one-step reaction method of Na₂WO₄·2H₂O, H₃PO₃, HNA, NH₂(CH₃)₂·HCl, and RE(NO₃)·6H₂O. Of meticulous concern is that HPO₃^2- was used as a template to construct tetrameric RE-substituted phospho(III)tungstates including mixed heteropolyoxotungstate building blocks. Their hybrid polyoxoanions are composed of two symmetrical [RE₂(NA)(HNA)(H₂O)₆(W₂O₄)(β-H₂P₂^IIIW₁₃O₄₉)(α-HPW₉O₃₃)]^11- units linked by RE-O-W bonds. The symmetrical unit consists of one peculiar heterometal nicotinic-acid-ornamented [RE₂(NA)(HNA)(W₂O₄)]⁹⁺ cluster connecting a pentavacant Dawson-like [β-H₂P₂W₁₃O₄₉]^12- and a trivacant Keggin [α-HPW₉O₃₃]^8- subunits. Furthermore, dimethyldioctadecylammonium chloride (DMDODA·Cl) was used to combine with 1-Nd in the CHCl₃-H₂O system through electrostatic interactions, leading to the 1-Nd@DMDODA composite material. The honeycomb-patterned film of the 1-Nd @DMDODA composite material was successfully constructed by using the breath figure method on a glassy carbon electrode, which can offer abundant binding sites to Au nanoparticles (nano-Au). Ulteriorly, Au-functionalized 1-Nd@DMDODA-modified electrode was utilized as an electrochemical sensor to detect ochratoxin A, showing a good detection limit of 1.19 pM.

Hexameric to Trimeric Lanthanide-Included Selenotungstates and Their 2D Honeycomb Organic-Inorganic Hybrid Films Used for Detecting Ochratoxin A

Two types of organic-inorganic hybrid structure-related lanthanide (Ln)-included selenotungstates (Ln-SeTs) [H₂N(CH₃)₂]₁₁Na₇[Ce₄(H₂PTCA)₂(H₂O)₁₂(HICA)]₂[SeW₄O₁₇]₂[W₂O₅]₄[SeW₉O₃₃]₄·64H₂O (1, H₃PTCA = 1,2,3-propanetricarboxylic acid, H₂ICA = itaconic acid) and [H₂N(CH₃)₂]₆Na₄[Ln₄SeW₈(H₂O)₁₄(H₂PTCA)₂O₂₈] [SeW₉O₃₃]₂·31H₂O [Ln = Pr³⁺ (2), Nd³⁺ (3)] were obtained by Ln nature control. The primary frameworks of 1-3 are composed of trivacant Keggin-type [B-α-SeW₉O₃₃]^8- and [SeW₄O_m]^n- [Ln = Ce³⁺ (1), m = 17, n = 6; Ln = Pr³⁺ (2), Nd³⁺ (3), m = 18, n = 8] fragments bridged by organic ligands and Ln clusters. Intriguingly, Ln nature results in the degradation of hexameric 1 to trimeric 2-3. Besides, 1@DMDSA and 3@DMDSA composites (DMDSA·Cl = dimethyl distearylammonium chloride) were prepared through the cation exchange method, which were then reorganized to form two-dimensional (2D) honeycomb thin films by the breath figure method. Using these honeycomb thin films as electrode materials, the aptasensors were further established by utilizing methylene blue as an indicator and cDNA and Au nanoparticles as signal amplifiers to enhance the response signal so as to realize the purpose of ochratoxin A (OTA) detection. This work provides a new platform for detecting OTA and explores the application potential of POM-based composites in biological and clinical analyses.

Multi-Nuclear Rare-Earth-Implanted Tartaric Acid-Functionalized Selenotungstates and Their Fluorescent and Magnetic Properties

A family of multinuclear rare-earth (RE)-implanted H₂tart^2--functionalized selenotungstates (STs) [H₂N(CH₃)₂]₁₃H{[W₂O₅(OH)₂(H₂tart)₂](H₂tart){[W₃O₆RE₂(H₂O)₆][SeW₉O₃₃]₂}₂}·31H₂O [RE = Eu³⁺ (1), Tb³⁺ (2), Dy³⁺ (3), Ho³⁺ (4), Y³⁺ (5); H₄tart = d-tartaric acid] have been afforded by a simple one-pot aqueous reaction and were structurally characterized. Intriguingly, their isomorphous organic-inorganic hybrid anion {[W₂O₅(OH)₂(H₂tart)₂](H₂tart){[W₃O₆RE₂(H₂O)₆][SeW₉O₃₃]₂}₂}^14- includes two sandwich-type {[W₃O₆[RE₂(H₂O)₆][SeW₉O₃₃]₂}^4- dimeric units with a W-O-RE heterometal core, which are further joined by two H₂tart^2--decorated dinuclear tungsten-oxo {W₂O₅(OH)₂(H₂tart)₂} clusters and a bridging H₂tart^2- ligand, contributing to a surprising Mobius band-like configuration. It is worth emphasizing that three H₂tart^2- ligands coordinate with tungsten centers rather than RE cations. For all we know, 1-5 delegate the infrequent RE-implanted STs functionalized by triplicate H₂tart^2- bridges. Furthermore, fluorescent performances of 1-4 as well as magnetic properties of 2-4 have been surveyed. The solid-state fluorescence emission spectra prove that each of them undoubtedly shows the characteristic emission peaks of RE cores, while alternating-current susceptibility measurements suggest field-induced single-molecule magnetic behavior in 3.