A Chemically Soldered Polyoxometalate Single-Molecule Transistor

Nuclear Magnetic Resonance Chemical Shift as a Probe for Single-Molecule Charge Transport

Existing modelling tools, developed to aid the design of efficient molecular wires and to better understand their charge-transport behaviour and mechanism, have limitations in accuracy and computational cost. Further research is required to develop faster and more precise methods that can yield information on how charge transport properties are impacted by changes in the chemical structure of a molecular wire. In this study, we report a clear semilogarithmic correlation between charge transport efficiency and nuclear magnetic resonance chemical shifts in multiple series of molecular wires, also accounting for the presence of chemical substituents. The NMR data was used to inform a simple tight-binding model that accurately captures the experimental single-molecule conductance values, especially useful in this case as more sophisticated density functional theory calculations fail due to inherent limitations. Our study demonstrates the potential of NMR spectroscopy as a valuable tool for characterising, rationalising, and gaining additional insights on the charge transport properties of single-molecule junctions.

An Orthogonal Conductance Pathway in Spiropyrans for Well-Defined Electrosteric Switching Single-Molecule Junctions

While a multitude of studies have appeared touting the use of molecules as electronic components, the design of molecular switches is crucial for the next steps in molecular electronics. In this work, single-molecule devices incorporating spiropyrans, made using break junction techniques, are described. Linear spiropyrans with electrode-contacting groups linked by alkynyl spacers to both the indoline and chromenone moieties have previously provided very low conductance values, and removing the alkynyl spacer has resulted in a total loss of conductance. An orthogonal T-shaped approach to single-molecule junctions incorporating spiropyran moieties in which the conducting pathway lies orthogonal to the molecule backbone is described and characterized. This approach has provided singlemolecule conductance features with good correlation to molecular length. Additional higher conducting states are accessible using switching induced by UV light or protonation. Theoretical modeling demonstrates that upon (photo)chemical isomerization to the merocyanine, two cooperating phenomena increase conductance: release of steric hindrance allows the conductance pathway to become more planar (raising the mid-bandgap transmission) and a bound state introduces sharp interference near the Fermi level of the electrodes similarly responding to the change in state. This design step paves the way for future use of spiropyrans in single-molecule devices and electrosteric switches.

Connectivity-Dependent Conductance of 2,2'-Bipyridine-Based Metal Complexes

The present work provides an insight into the effect of connectivity isomerization of metal-2,2'-bipyridine complexes. For that purpose, two new 2,2'-bipyridine (bpy) ligand systems, 4,4'-bis(4-(methylthio)phenyl)-2,2'-bipyridine (Lmeta) and 5,5'-bis(3,3-dimethyl-2,3-dihydrobenzothiophen-5-yl)-2,2'-bipyridine (Lpara) were synthesized and coordinated to rhenium and manganese to obtain the corresponding complexes MnLmeta(CO)3Br, ReLmeta(CO)3Br, MnLpara(CO)3Br, MoLpara(CO)4 and ReLpara(CO)3Br. The experimental and theoretical results revealed that coordination to the para system, i.e., the metal ion peripheral to the conductance path, gave a slightly increased conductance compared to the free ligand attributed to the reduced highest occupied molecular orbital (HOMO)-least unoccupied molecular orbital (LUMO) gap. The meta-based system formed a destructive quantum interference feature that reduced the conductance of a S···S contacted junction to below 10-5.5Go, reinforcing the importance of contact group connectivity for molecular wire conductance.

An Unusual Bismuth-Antimony-Europium Cluster-Imbedded Polyoxotungstate and Its Bidirectional Luminescence Detection

An unprecedented aggregate formed by two bismuth-antimony-europium cluster-imbedded tungsten-oxo clusters and one Krebs-type polyoxotungstate linker [H2N(CH3)2]14Na30H6[W4O10][B-β-BiW9O33]2{[Bi5.35Sb0.65Eu3O9(H2O)9][B-α-SbW9O33]3}2·124H2O (1) was prepared. The polyoxoanion skeleton of 1 contains a Krebs-type polyoxotungstate [W4O10][B-β-BiW9O33]2}14- ({Bi2W22}) (1a) as a linker that offers six active coordinate O atoms (two μ3-O and four μ2-O atoms) to grasp two Bi-Sb-Eu cluster-imbedded tungsten-oxo clusters {[Bi5.35Sb0.65Eu3O9(H2O)9][B-α-SbW9O33]3}18- (1b) through Bi-O-W and Sb-O-W bonds. 1b comprises an unprecedented nona-nuclearity Bi-Sb-Eu [Bi5.35Sb0.65Eu3O9(H2O)9]9+ cluster encircled by three trivacant [B-α-SbW9O33]9-segments in a triangular motif through Eu-O-W, Sb-O-W, and Bi-O-W linkages into a trilobal trimer. Moreover, a bidirectional detection method by using 1 as an effective luminescence probe was proposed to recognize both Mn2+ and CO32- through an "on-off-on" mode. 1 can be used as an "on-off" luminescent sensor to detect Mn2+ ions in aqueous solution. The limit of detection was 0.05 μM (9 × 10-6 mg L-1), which is much lower than the World Health Organization (WHO) guideline for Mn2+ concentration in drinking water (0.05 mg L-1). Then the Mn2+-quenching system can be used as an "off-on" sensor to detect CO32- in water system. This work provides a new research idea for the application of rare-earth-imbedded polyoxotungstate-based materials in the field of optical smart detection.

Supramolecular Transistors with Quantum Interference Effect

The charge transport through supramolecular junctions exhibits unique quantum interference (QI) effects, which provide an opportunity for the design of supramolecular transistors. Benefiting from the configuration dependence of QI, configuration control of the supramolecular assemblies to demonstrate the QI features is a key but challenging step. In this work, we fabricated the supramolecular transistors and investigated the charge transport through the conducting channel of the individual π-stacked thiophene/phenylene co-oligomers (TPCOs) using the electrochemically gated scanning tunneling microscope break junction technique. We controlled the configuration of the supramolecular channel and switched the QI features between the anti-resonance and resonance states of the supramolecular channels. We observed the supramolecular transistor with its on/off ratio above 103 (∼1300), a high gating efficiency of ∼165 mV/dec, a low off-state leakage current of ∼30 pA, and the channel length scaled down to <2.0 nm. Density functional theory calculations suggested that the QI features in π-stacked TPCOs vary depending on the supramolecular architecture and can be manipulated efficiently by fine-tuning the supramolecular configurations. This work reveals the potential of the supramolecular channels for molecular electronics and provides a fundamental understanding of intermolecular charge transport.

Ready-to-be-addressed oxo-clusters: individualized, periodically organized and separated from the substrate

Clusters and oxo-clusters are drawing attention for their amazing physical properties, especially at the scale of the single molecule. However, chemical methods to organize them individually on a surface are still lacking. In this study we show that it is possible to periodically organize individual polyoxometalates thanks to their ordering by a new supramolecular assembly.

Single-Molecule Junction Formation in Deep Eutectic Solvents with Highly Effective Gate Coupling

The environment surrounding a molecular junction affects its charge-transport properties and, therefore, must be chosen with care. In the case of measurements in liquid media, the solvent must provide good solvation, grant junction stability, and, in the case of electrolyte gating experiments, allow efficient electrical coupling to the gate electrodes through control of the electrical double layer. We evaluated in this study the deep eutectic solvent mixture (DES) ethaline, which is a mixture of choline chloride and ethylene glycol (1:2), for single-molecule junction fabrication with break-junction techniques. In ethaline, we were able to (i) measure challenging and poorly soluble molecular wires, exploiting the improved solvation capabilities offered by DESs, and (ii) efficiently apply an electrostatic gate able to modulate the conductance of the junction by approximately an order of magnitude within a ∼1 V potential window. The electrochemical gating results on a Au-VDP-Au junction follow exceptionally well the single-level modeling with strong gate coupling (where VDP is 1,2-di(pyridine-4-yl)ethene). Ethaline is also an ideal solvent for the measurement of very short molecular junctions, as it grants a greatly reduced snapback distance of the metallic electrodes upon point-contact rupture. Our work demonstrates that DESs are viable alternatives to often relatively expensive ionic liquids, offering good versatility for single-molecule electrical measurements.

Molecular Electronics: Creating and Bridging Molecular Junctions and Promoting Its Commercialization

Molecular electronics is driven by the dream of expanding Moore's law to the molecular level for next-generation electronics through incorporating individual or ensemble molecules into electronic circuits. For nearly 50 years, numerous efforts have been made to explore the intrinsic properties of molecules and develop diverse fascinating molecular electronic devices with the desired functionalities. The flourishing of molecular electronics is inseparable from the development of various elegant methodologies for creating nanogap electrodes and bridging the nanogap with molecules. This review first focuses on the techniques for making lateral and vertical nanogap electrodes by breaking, narrowing, and fixed modes, and highlights their capabilities, applications, merits, and shortcomings. After summarizing the approaches of growing single molecules or molecular layers on the electrodes, the methods of constructing a complete molecular circuit are comprehensively grouped into three categories: 1) directly bridging one-molecule-electrode component with another electrode, 2) physically bridging two-molecule-electrode components, and 3) chemically bridging two-molecule-electrode components. Finally, the current state of molecular circuit integration and commercialization is discussed and perspectives are provided, hoping to encourage the community to accelerate the realization of fully scalable molecular electronics for a new era of integrated microsystems and applications.

Enhanced charge transport across molecule-nanoparticle-molecule sandwiches

The electrical properties of large area molecular devices consisting of gold nanoparticles (GNPs) sandwiched between a double layer of alkanedithiol linkers have been examined. These devices have been fabricated by a facile bottom-up assembly in which an alkanedithiol monolayer is first self-assembled on an underlying gold substrate followed by nanoparticle adsorption and then finally assembly of the top alkanedithiol layer. These devices are then sandwiched between the bottom gold substrates and a top eGaIn probe contact and current-voltage (I-V) curves recorded. Devices have been fabricated with 1,5-pentanedithiol, 1,6-hexanedithiol, 1,8-octanedithiol and 1,10-decanedithiol linkers. In all cases the electrical conductance of the double SAM junctions with GNPs is higher than the corresponding and much thinner single alkanedithiol SAM. Competing models for this enhanced conductance are discussed and it is suggested to have a topological origin arising from how the devices assemble or structure during the fabrication, which gives more efficient cross device electron transport pathways without the GNPs producing short circuits.

Design of Pyrrole-Based Gate-Controlled Molecular Junctions Optimized for Single-Molecule Aflatoxin B1 Detection

Food contamination by aflatoxins is an urgent global issue due to its high level of toxicity and the difficulties in limiting the diffusion. Unfortunately, current detection techniques, which mainly use biosensing, prevent the pervasive monitoring of aflatoxins throughout the agri-food chain. In this work, we investigate, through ab initio atomistic calculations, a pyrrole-based Molecular Field Effect Transistor (MolFET) as a single-molecule sensor for the amperometric detection of aflatoxins. In particular, we theoretically explain the gate-tuned current modulation from a chemical-physical perspective, and we support our insights through simulations. In addition, this work demonstrates that, for the case under consideration, the use of a suitable gate voltage permits a considerable enhancement in the sensor performance. The gating effect raises the current modulation due to aflatoxin from 100% to more than 103÷104%. In particular, the current is diminished by two orders of magnitude from the μA range to the nA range due to the presence of aflatoxin B1. Our work motivates future research efforts in miniaturized FET electrical detection for future pervasive electrical measurement of aflatoxins.

Electrochemically controlled rectification in symmetric single-molecule junctions

Single-molecule electrochemical science has advanced over the past decades and now extends well beyond molecular imaging, to molecular electronics functions such as rectification and amplification. Rectification is conceptually the simplest but has involved mostly challenging chemical synthesis of asymmetric molecular structures or asymmetric materials and geometry of the two enclosing electrodes. Here we propose an experimental and theoretical strategy for building and tuning in situ (in operando) rectification in two symmetric molecular structures in electrochemical environment. The molecules were designed to conduct electronically via either their lowest unoccupied molecular orbital (LUMO; electron transfer) or highest occupied molecular orbital (HOMO; "hole transfer"). We used a bipotentiostat to control separately the electrochemical potential of the tip and substrate electrodes of an electrochemical scanning tunneling microscope (EC-STM), which leads to independent energy alignment of the STM tip, the molecule, and the STM substrate. By creating an asymmetric energy alignment, we observed single-molecule rectification of each molecule within a voltage range of ±0.5 V. By varying both the dominating charge transporting LUMO or HOMO energy and the electrolyte concentration, we achieved tuning of the polarity as well as the amplitude of the rectification. We have extended an earlier proposed theory that predicts electrolyte-controlled rectification to rationalize all the observed in situ rectification features and found excellent agreement between theory and experiments. Our study thus offers a way toward building controllable single-molecule rectifying devices without involving asymmetric molecular structures.

2,7- and 4,9-Dialkynyldihydropyrene Molecular Switches: Syntheses, Properties, and Charge Transport in Single-Molecule Junctions

This paper describes the syntheses of several functionalized dihydropyrene (DHP) molecular switches with different substitution patterns. Regioselective nucleophilic alkylation of a 5-substituted dimethyl isophthalate allowed the development of a workable synthetic protocol for the preparation of 2,7-alkyne-functionalized DHPs. Synthesis of DHPs with surface-anchoring groups in the 2,7- and 4,9-positions is described. The molecular structures of several intermediates and DHPs were elucidated by X-ray single-crystal diffraction. Molecular properties and switching capabilities of both types of DHPs were assessed by light irradiation experiments, spectroelectrochemistry, and cyclic voltammetry. Spectroelectrochemistry, in combination with density functional theory (DFT) calculations, shows reversible electrochemical switching from the DHP forms to the cyclophanediene (CPD) forms. Charge-transport behavior was assessed in single-molecule scanning tunneling microscope (STM) break junctions, combined with density functional theory-based quantum transport calculations. All DHPs with surface-contacting groups form stable molecular junctions. Experiments show that the molecular conductance depends on the substitution pattern of the DHP motif. The conductance was found to decrease with increasing applied bias.

An isolated doughnut-like molybdenum(V) cobalto-phosphate cluster exhibiting excellent photocatalytic performance for carbon dioxide conversion

An isolated doughnut-like molybdenum(V) cobalto-phosphate cluster with the formula (C₁₁NH₁₀)₂{[Co(H₂O)₆]@[H₂₉Co₁₆Mo₁₆(H₂O)₁₆(PO₄)₂₄O₃₆]}(H₂PO₄)·25H₂O has been successfully synthesized by a hydrothermal method. Single crystal X ray diffraction analysis shows that four {Co₄O₆₀} tetramers and eight {Mo₂O₁₀} dimers are linked by oxygen atoms and phosphate groups to construct a doughnut-type structure for [Co@{Co₁₆Mo₁₆}], in which one [Co^II(H₂O)₆]²⁺ octahedron is enclosed. More importantly, [Co@{Co₁₆Mo₁₆}] exhibits promising photocatalytic performance for CO₂ reduction with the CO formation rate of 6764.3 μmol g^-1 h^-1 and the selectivity of 96.89%. In addition, the cycling test indicated that [Co@{Co₁₆Mo₁₆}] can be reused for at least four cycles without significant loss of catalytic activity. The result of this work may provide new insight for the synthesis of highly efficient POM-based photocatalysts for CO₂ reduction.

Redox-Addressable Single-Molecule Junctions Incorporating a Persistent Organic Radical

Integrating radical (open-shell) species into non-cryogenic nanodevices is key to unlocking the potential of molecular electronics. While many efforts have been devoted to this issue, in the absence of a chemical/electrochemical potential the open-shell character is generally lost in contact with the metallic electrodes. Herein, single-molecule devices incorporating a 6-oxo-verdazyl persistent radical have been fabricated using break-junction techniques. The open-shell character is retained at room temperature, and electrochemical gating permits in situ reduction to a closed-shell anionic state in a single-molecule transistor configuration. Furthermore, electronically driven rectification arises from bias-dependent alignment of the open-shell resonances. The integration of radical character, transistor-like switching, and rectification in a single molecular component paves the way to further studies of the electronic, magnetic, and thermoelectric properties of open-shell species.

Electrochemical gating for single-molecule electronics with hybrid Au|graphene contacts

The single-molecular conductance of a redox active viologen molecular bridge between Au|graphene electrodes has been studied in an electrochemical gating configuration in an ionic liquid medium. A clear "off-on-off" conductance switching behaviour has been achieved through gating of the redox state when the electrochemical potential is swept. The Au|viologen|graphene junctions show single-molecule conductance maxima centred close to the equilibrium redox potentials for both reduction steps. The peak conductance of Au|viologen|graphene junctions during the first reduction is significantly higher than that of previously measured Au|viologen|Au junctions. This shows that even though the central viologen moiety is not directly linked to the enclosing electrodes, substituting one gold contact for a graphene one nevertheless has a significant impact on junction conductance values. The experimental data was compared against two theoretical models, namely a phase coherent tunnelling and an incoherent "hopping" model. The former is a simple gating monoelectronic model within density functional theory (DFT) which discloses the charge state evolution of the molecule with electrode potential. The latter model is the collective Kuznetsov Ulstrup model for 2-step sequential charge transport through the redox centre in the adiabatic limit. The comparison of both models to the experimental data is discussed for the first time. This work opens perspectives for graphene-based molecular transistors with more effective gating and fundamental understanding of electrochemical electron transfer at the single molecular level.

Mechanoresistive single-molecule junctions

Single-molecule junctions - devices fabricated by electrically connecting a single molecule to two electrodes - can respond to a variety of stimuli, that include electrostatic/electrochemical gating, light, other chemical species, and mechanical forces. When the latter is used, the device becomes mechanoresistive which means that its electrical resistance/conductance changes upon application of a mechanical stress. The mechanoresistive phenomenon can arise at the metal-molecule interface or it can be embedded in the molecular backbone, and several strategies to attain high reproducibility, high sensitivity and reversible behaviour have been developed over the years. These devices offer a unique insight on the process of charge transfer/transport at the metal/molecule interface, and have potential for applications as nanoelectromechanical systems, integrating electrical and mechanical functionality at the nanoscale. In this review, the status of the field is presented, with a focus on those systems that proved to have reversible behaviour, along with a discussion on the techniques used to fabricate and characterise mechanoresistive devices.

Two Cu(i)-based inorganic–organic complexes assembled with polyoxometalate and thiacalix[4]arene for efficient catalytic reactions

Two Cu(i)-based inorganic–organic complexes were synthesized, which can be used as high-efficiency heterogeneous catalysts for ODS and AAC reactions, respectively.

Phase transitions induced by exchange coupling, magnetic field, and temperature in a strongly correlated molecular trimer with triangular topology

Regulating the physical properties such as the quantum phase and the Kondo effect of molecular electronic devices near critical points may play a key role in increasing the robustness of...

The Intrinsic Charge Carrier Behaviors and Applications of Polyoxometalate Clusters Based Materials

Polyoxometalates (POMs) are a series of molecular metal oxide clusters, which span the two domains of solutes and solid metal oxides. The unique characters of POMs in structure, geometry, and adjustable redox properties have attracted widespread attention in functional material synthesis, catalysis, electronic devices, and electrochemical energy storage and conversion. This review is focused on the links between the intrinsic charge carrier behaviors of POMs from a chemistry-oriented view and their recent ground-breaking developments in related areas. First, the advantageous charge transfer behaviors of POMs in molecular-level electronic devices are summarized. Solar-driven, thermal-driven, and electrochemical-driven charge carrier behaviors of POMs in energy generation, conversion and storage systems are also discussed. Finally, present challenges and fundamental insights are discussed as to the advanced design of functional systems based upon POM building blocks for their possible emerging application areas.

Polyoxoplatinates as covalently dynamic electron sponges and molecular electronics materials

In organic systems, dynamic covalent chemistry provides an adaptive approach (i.e., "covalent dynamics") where thermodynamic equilibria are used to tailor structural and electronic changes in molecular assemblies. The covalent dynamics finds utility in the design of novel self-healing materials, sensors, and actuators. Herein, using density functional theory (DFT) we explore the structural, electronic and transport properties of the Pt-based polyoxometalate (POM) [Pt^III ₁₂O₈(SO₄)₁₂]^4- and its derivatives. The latter POM has six redox responsive {O-Pt-Pt-O} moieties and prospects for storage of up to twelve electrons, thus exemplifying how dynamic covalent chemistry may manifest itself in fully inorganic systems. Simulations of the Au/POM/Au junction show that the electron conduction strongly depends on the redox of the POM but more weakly on its rotations with respect to the Au surface. Moreover, the POM shows promising spin-polarized current behaviour, which can be modulated using bias and gate voltages.

Single-atom control of electrical conductance and thermopower through single-cluster junctions

The control of single atoms offers fundamental insight into understanding the charge transport through single clusters, and the atomic precision of the clusters provides the opportunity to manipulate the charge transport even at the single-atom level. Herein, we designed and investigated the electrical conductance and thermopower of Anderson-type polyoxometalate (POM) clusters with single-atom variation using the scanning tunneling microscopy break-junction (STM-BJ) technique. Our results show the electrical conductance of single clusters can be changed by an order of magnitude by substituting different center-metal atoms, and the electrical conductance of clusters shows different bias-dependence. Furthermore, the Seebeck coefficients of the POM clusters also can be significantly changed by the center-metal atoms. The non-equilibrium quantum transport calculations reveal that the electrostatic potential profile is non-uniformly dependent on the center-metal atoms. This leads to gating of electrical conductance by bias voltage. This supports the tuning of thermopower and bias dependent transmission spectra. This work provides the fundamental understanding of single-atom control of charge transport in POM single-cluster junctions.

Anderson-type polyoxometalates: from structures to functions

Anderson-type polyoxometalates (POMs) are one of the most important groups of the POM family. In the past decade, the functionalization of Anderson-type POMs has achieved significant progress and these materials have already shown unique charm in catalysis, molecular devices, energy materials, and inorganic biochemical drugs. In particular, their highly flexible topological structure and diverse functionalization methods make them the most convenient and universal platforms for rational design and controllable synthesis. This review provides a deep discussion on the recent progress in the synthetic methodology, structural exploration, and promising applications of Anderson-type POMs. It also summarizes the latest research directions and provides future prospects.

{P2V3W15}-Polyoxometalates Functionalized with Phthalocyaninato Y and Yb Moieties

A tris(alkoxo)pyridine-augmented Wells-Dawson polyoxometalate (nBu₄N)₆[WD-Py] (WD = P₂V₃W₁₅O₅₉(OCH₂)₃C, Py = C₅H₄N) was functionalized with phthalocyaninato metal moieties (MPc where M = Y or Yb and Pc = C₃₂H₁₆N₈) to afford (nBu₄N)₄[HWD-Py(MPc)] compounds. High-resolution mass spectrometry was used to detect and identify the hybrid assembly. The magnetism studies reveal substantial differences between M = Yb (monomeric, single-ion paramagnetism) and M = Y (containing dimers, radical character). The results of electronic paramagnetic resonance spectroscopy, SQUID magnetometry, and magnetochemical calculations indicate the presence of intramolecular charge transfer from the MPc moiety to the polyoxometalate and of intermolecular charge transfer from the MPc moiety of one molecule to the polyoxometalate unit of another molecule. These compounds with identified V^IV ions represent unique examples of transition-metal/lanthanide complex-POM hybrid compounds with nonphotoinduced charge transfer between electron donor and acceptor centers.

TiO x /Pt3Ti(111) surface-directed formation of electronically responsive supramolecular assemblies of tungsten oxide clusters

Highly ordered titanium oxide films grown on a Pt₃Ti(111) alloy surface were utilized for the controlled immobilization and tip-induced electric field-triggered electronic manipulation of nanoscopic W₃O₉ clusters. Depending on the operating conditions, two different stable oxide phases, z'-TiO _x and w'-TiO _x , were produced. These phases show a strong effect on the adsorption characteristics and reactivity of W₃O₉ clusters, which are formed as a result of thermal evaporation of WO₃ powder on the complex TiO _x /Pt₃Ti(111) surfaces under ultra-high vacuum conditions. The physisorbed tritungsten nano-oxides were found as isolated single units located on the metallic attraction points or as supramolecular self-assemblies with a W₃O₉-capped hexagonal scaffold of W₃O₉ units. By applying scanning tunneling microscopy to the W₃O₉-(W₃O₉)₆ structures, individual units underwent a tip-induced reduction to W₃O₈. At elevated temperatures, agglomeration and growth of large WO₃ islands, which thickness is strongly limited to a maximum of two unit cells, were observed. The findings boost progress toward template-directed nucleation, growth, networking, and charge state manipulation of functional molecular nanostructures on surfaces using operando techniques.

Core–shell carbon colloid sphere@phosphotungstic acid/CdS as a Z-scheme heterojunction with synergistic adsorption, photothermal and photocatalytic performance

Core–shell carbon colloid sphere@phosphotungstic acid/CdS exhibits excellent visible-light-driven photocatalytic performance, which is due to the Z-scheme heterojunction favoring the charge transfer and spatial charge separation and the photothermal effect.

A Chemically Soldered Polyoxometalate Single-Molecule Transistor

Polyoxometalates have been proposed in the literature as nanoelectronic components, where they could offer key advantages with their structural versatility and rich electrochemistry. Apart from a few studies on their ensemble behaviour (as monolayers or thin films), this potential remains largely unexplored. We synthesised a pyridyl-capped Anderson-Evans polyoxometalate and used it to fabricate single-molecule junctions, using the organic termini to chemically "solder" a single cluster to two nanoelectrodes. Operating the device in an electrochemical environment allowed us to probe charge transport through different oxidation states of the polyoxometalate, and we report here an efficient three-state transistor behaviour. Conductance data fits a quantum tunnelling mechanism with different charge-transport probabilities through different charge states. Our results show the promise of polyoxometalates in nanoelectronics and give an insight on their single-entity electrochemical behaviour.

Two new isolated Zn-ε-Keggin clusters modified by conjugated organic ligands with decent electrocatalytic and third-order NLO properties

Compound 2 is the first isolated Zn₅PMo₁₂ cluster, and the two Zn-ε-Keggin-based compounds display excellent electrocatalytic and third-order NLO properties.