Boosting Zinc Hybrid Supercapacitor Performance via Thiol Functionalization of Graphene-Based Cathodes

Zinc hybrid supercapacitors (Zn-HSCs) hold immense potential toward the next-generation energy storage systems, effectively spanning the divide between conventional lithium-ion batteries (LIBs) and supercapacitors. Unfortunately, the energy density of most of Zn-HSCs has not yet rivalled the levels observed in LIBs. The electrochemical performance of aqueous Zn-HSCs can be enhanced through the chemical functionalization of graphene-based cathode materials with thiol moieties as they will be highly suitable for favoring Zn2+ adsorption/desorption. Here, a single-step reaction is employed to synthesize thiol-functionalized reduced graphene oxide (rGOSH), incorporating both oxygen functional groups (OFGs) and thiol functionalities, as demonstrated by X-ray photoelectron spectroscopy (XPS) studies. Electrochemical analysis reveals that rGOSH cathodes exhibit a specific capacitance (540 F g-1) and specific capacity (139 mAh g-1) at 0.1 A g-1 as well as long-term stability, with over 92% capacitance retention after 10 000 cycles, outperforming chemically reduced graphene oxide (CrGO). Notably, rGOSH electrodes displayed an exceptional maximum energy density of 187.6 Wh kg-1 and power density of 48.6 kW kg-1. Overall, this study offers an unprecedented powerful strategy for the design and optimization of cathode materials, paving the way for efficient and sustainable energy storage solutions to meet the increasing demands of modern energy applications.

Molecular Connectors Boosting the Performance of MoS2 Cathodes in Zinc-Ion Batteries

Zinc-ion batteries (ZIBs) are promising energy storage systems due to high energy density, low-cost, and abundant availability of zinc as a raw material. However, the greatest challenge in ZIBs research is lack of suitable cathode materials that can reversibly intercalate Zn2+ ions. 2D layered materials, especially MoS2 -based, attract tremendous interest due to large surface area and ability to intercalate/deintercalate ions. Unfortunately, pristine MoS2 obtained by traditional protocols such as chemical exfoliation or hydrothermal/solvothermal methods exhibits limited electronic conductivity and poor chemical stability upon charge/discharge cycling. Here, a novel molecular strategy to boost the electrochemical performance of MoS2 cathode materials for aqueous ZIBs is reported. The use of dithiolated conjugated molecular pillars, that is, 4,4'-biphenyldithiols, enables to heal defects and crosslink the MoS2 nanosheets, yielding covalently bridged networks (MoS2 -SH2) with improved ionic and electronic conductivity and electrochemical performance. In particular, MoS2 -SH2 electrodes display high specific capacity of 271.3 mAh g-1 at 0.1 A g-1 , high energy density of 279 Wh kg-1 , and high power density of 12.3 kW kg-1 . With its outstanding rate capability (capacity of 148.1 mAh g-1 at 10 A g-1 ) and stability (capacity of 179 mAh g-1 after 1000 cycles), MoS2 -SH2 electrodes outperform other MoS2 -based electrodes in ZIBs.

MOF (UiO-66-NH2)@COF (TFP-TABQ) hybrids via on-surface condensation reactions for sustainable energy storage

Core-shell MOF@COF hybrids were synthesized via subsequent modification of MOF UiO-66-NH2 with 1,3,5-triformylphloroglucinol (TFP) and 2,3,5,6-tetraaminobenzoquinone (TABQ). The hybrids exhibited significant surface area (236 m2 g-1) and outstanding electrochemical performance (103 F g-1 at 0.5 A g-1), surpassing both COFs and MOFs, thereby showcasing the potential of on-surface condensation reactions for developing high-performance energy storage devices.

Construction of Multi-Stimuli Responsive Highly Porous Switchable Frameworks by In Situ Solid-State Generation of Spiropyran Switches

Stimuli-responsive molecular systems support within permanently porous materials offer the opportunity to host dynamic functions in multifunctional smart materials. However, the construction of highly porous frameworks featuring external-stimuli responsiveness, for example by light excitation, is still in its infancy. Here a general strategy is presented to construct spiropyran-functionalized highly porous switchable aromatic frameworks by modular and high-precision anchoring of molecular hooks and an innovative in situ solid-state grafting approach. Three spiropyran-grafted frameworks bearing distinct functional groups exhibiting various stimuli-responsiveness are generated by two-step post-solid-state synthesis of a parent indole-based material. The quantitative transformation and preservation of high porosity are demonstrated by spectroscopic and gas adsorption techniques. For the first time, a highly efficient strategy is provided to construct multi-stimuli-responsive, yet structurally robust, spiropyran materials with high pore capacity which is proved essential for the reversible and quantitative isomerization in the bulk as demonstrated by solid-state NMR spectroscopy. The overall strategy allows to construct dynamic materials that undergoes reversible transformation of spiropyran to zwitterionic merocyanine, by chemical and physical stimulation, showing potential for pH active control, responsive gas uptake and release, contaminant removal, and water harvesting.

Enhancing the Carrier Transport in Monolayer MoS2 through Interlayer Coupling with 2D Covalent Organic Frameworks

The coupling of different 2D materials (2DMs) to form van der Waals heterostructures (vdWHs) is a powerful strategy for adjusting the electronic properties of 2D semiconductors, for applications in opto-electronics and quantum computing. 2D molybdenum disulfide (MoS2 ) represents an archetypical semiconducting, monolayer thick versatile platform for the generation of hybrid vdWH with tunable charge transport characteristics through its interfacing with molecules and assemblies thereof. However, the physisorption of (macro)molecules on 2D MoS2 yields hybrids possessing a limited thermal stability, thereby jeopardizing their technological applications. Herein, the rational design and optimized synthesis of 2D covalent organic frameworks (2D-COFs) for the generation of MoS2 /2D-COF vdWHs exhibiting strong interlayer coupling effects are reported. The high crystallinity of the 2D-COF films makes it possible to engineer an ultrastable periodic doping effect on MoS2 , boosting devices' field-effect mobility at room temperature. Such a performance increase can be attributed to the synergistic effect of the efficient interfacial electron transfer process and the pronounced suppression of MoS2 's lattice vibration. This proof-of-concept work validates an unprecedented approach for the efficient modulation of the electronic properties of 2D transition metal dichalcogenides toward high-performance (opto)electronics for CMOS digital circuits.

Controlling the Formation of Electroactive Graphene-Based Cementitious Composites: Towards Structural Health Monitoring of Civil Structures

The development of composites combining multiple components each one imparting a specific function to the ensemble is highly sought after for disruptive applications in chemistry and materials science, with a particular importance for the realization of smart structures. Here, we report on the development of an unprecedented multifunctional cementitious composite incorporating reduced graphene oxide (rGO). By design, this material features significantly enhanced electrical properties while retaining the excellent cement's hydration and microstructure. The multiscale investigation on the chemical and physical properties of the dispersion made it possible to establish an efficient preparation protocol for rGO aqueous dispersion as well as rGO-based cementitious composites using a commercial poly(carboxylate ether)-based superplasticizer. The conduction mechanisms within the matrix of rGO containing mortars were unraveled by electrochemical impedance spectroscopy revealing conductive paths originating from bulk cement matrix and rGO nanosheets in composites with rGO loadings as low as 0.075 wt. %. For this rGO loading, we observed the reduction of the resistivity of bulk cement mortar layers from 18.3 MΩ cm to 2.8 MΩ cm. Moreover, the addition of 0.2 wt. % of rGO resulted in the formation of rGO conductive paths with the resistivity of 51.1 kΩ cm. These findings represent a major step forward towards the practical application of graphene-based materials in structural health monitoring of concrete structures.

High Selectivity and Sensitivity in Chemiresistive Sensing of Co(II) Ions with Liquid-Phase Exfoliated Functionalized MoS2 : A Supramolecular Approach

Chemical sensing of water contamination by heavy metal ions is key as it represents a most severe environmental problem. Liquid-phase exfoliated two-dimensional (2D) transition metal dichalcogenides (TMDs) are suitable candidates for chemical sensing thanks to their high surface-to-volume ratio, sensitivity, unique electrical characteristics, and scalability. However, TMDs lack selectivity due to nonspecific analyte-nanosheet interactions. To overcome this drawback, defect engineering enables controlled functionalization of 2D TMDs. Here, ultrasensitive and selective sensors of cobalt(II) ions via the covalent functionalization of defect-rich MoS2 flakes with a specific receptor, 2,2':6',2″-terpyridine-4'-thiol is developed. A continuous network is assembled by healing of MoS2 sulfur vacancies in a tailored microfluidic approach, enabling high control over the assembly of thin and large hybrid films. The Co2+ cations complexation represents a powerful gauge for low concentrations of cationic species which can be best monitored in a chemiresisitive ion sensor, featuring a 1 pm limit of detection, sensing in a broad concentration range (1 pm - 1 µm) and sensitivity as high as 0.308 ± 0.010 lg([Co2+ ])-1 combined with a high selectivity towards Co2+ over K+ , Ca2+ , Mn2+ , Cu2+ , Cr3+ , and Fe3+ cations. This supramolecular approach based on highly specific recognition can be adapted for sensing other analytes through specific ad-hoc receptors.

A comparative investigation of the chemical reduction of graphene oxide for electrical engineering applications

The presence of oxygen-containing functional groups on the basal plane and at the edges endows graphene oxide (GO) with an insulating nature, which makes it rather unsuitable for electronic applications. Fortunately, the reduction process makes it possible to restore the sp2 conjugation. Among various protocols, chemical reduction is appealing because of its compatibility with large-scale production. Nevertheless, despite the vast number of reported chemical protocols, their comparative assessment has not yet been the subject of an in-depth investigation, rendering the establishment of a structure-performance relationship impossible. We report a systematic study on the chemical reduction of GO by exploring different reducing agents (hydrazine hydrate, sodium borohydride, ascorbic acid (AA), and sodium dithionite) and reaction times (2 or 12 hours) in order to boost the performance of chemically reduced GO (CrGO) in electronics and in electrochemical applications. In this work, we provide evidence that the optimal reduction conditions should vary depending on the chosen application, whether it is for electrical or electrochemical purposes. CrGO exhibiting a good electrical conductivity (>1800 S m-1) can be obtained by using AA (12 hours of reaction), Na2S2O4 and N2H4 (independent of the reaction time). Conversely, CrGO displaying a superior electrochemical performance (specific capacitance of 211 F g-1, and capacitance retention >99.5% after 2000 cycles) can be obtained by using NaBH4 (12 hours of reaction). Finally, the compatibility of the different CrGOs with wearable and flexible electronics is also demonstrated using skin irritation tests. The strategy described represents a significant advancement towards the development of environmentally friendly CrGOs with ad hoc properties for advanced applications in electronics and energy storage.

Dynamic Cages-Towards Nanostructured Smart Materials

The interest in capsular assemblies such as dynamic organic and coordination cages has blossomed over the last decade. Given their chemical and structural variability, these systems have found applications in diverse fields of research, including energy conversion and storage, catalysis, separation, molecular recognition, and live-cell imaging. In the exploration of the potential of these discrete architectures, they are increasingly being employed in the formation of more complex systems and smart materials. This Review highlights the most promising pathways to overcome common drawbacks of cage systems (stability, recovery) and discusses the most promising strategies for their hybridization with systems featuring various dimensionalities. Following the description of the most recent advances in the fabrication of zero to three-dimensional cage-based systems, this Review will provide the reader with the structure-dependent relationship between the employed cages and the properties of the materials.

Covalently Functionalized MXenes for Highly Sensitive Humidity Sensors

Transition metal carbides and nitrides (MXenes) are an emerging class of 2D materials, which are attracting ever-growing attention due to their remarkable physicochemical properties. The presence of various surface functional groups on MXenes' surface, e.g., F, O, OH, Cl, opens the possibility to tune their properties through chemical functionalization approaches. However, only a few methods have been explored for the covalent functionalization of MXenes and include diazonium salt grafting and silylation reactions. Here, an unprecedented two-step functionalization of Ti3 C2 Tx MXenes is reported, where (3-aminopropyl)triethoxysilane is covalently tethered to Ti3 C2 Tx and serves as an anchoring unit for subsequent attachment of various organic bromides via the formation of CN bonds. Thin films of Ti3 C2 Tx functionalized with linear chains possessing increased hydrophilicity are employed for the fabrication of chemiresistive humidity sensors. The devices exhibit a broad operation range (0-100% relative humidity), high sensitivity (0.777 or 3.035), a fast response/recovery time (0.24/0.40 s ΔH-1 , respectively), and high selectivity to water in the presence of saturated vapors of organic compounds. Importantly, our Ti3 C2 Tx -based sensors display the largest operating range and a sensitivity beyond the state of the art of MXenes-based humidity sensors. Such outstanding performance makes the sensors suitable for real-time monitoring applications.

New Anderson-Based Polyoxometalate Covalent Organic Frameworks as Electrodes for Energy Storage Boosted Through Keto-Enol Tautomerization

The unique electrochemical properties of polyoxometalates (POMs) render them ideal components for the fabrication of next-generation high-performance energy storage systems. However, their practical applications have been hindered by their high solubility in common electrolytes. This problem can be overcome by the effective hybridization of POMs with other materials. Here we present the design and synthesis of two novel polyoxometalate-covalent organic frameworks (POCOF) via one-pot solvothermal strategy between an amino-functionalized Anderson-type POM and a trialdehyde-based building unit. We show that structural and functional complexity can be enriched by adding hydroxyl groups in the 2,4,6 position to the benzene-1,3,5-tricarbaldehyde allowing to exploit for the first time in POCOFs keto-enol tautomerization as additional feature to impart greater chemical stability to the COFs and enhanced properties leading to large specific surface area (347 m2/g) and superior electrochemical performance of POCOF-1 electrodes, when compared with POCOF-2 electrodes that possess only imine-type linkage and with pristine POM electrodes. Specifically, POCOF-1 electrodes display remarkable specific, areal, and volumetric capacitance (125 F/g, 248 mF/cm2 and 41.9 mF/cm3, respectively) at a current density of 0.5 A/g, a maximum energy density (56.2 Wh/kg), a maximum power density (3.7 kW/kg) and an outstanding cyclability (90% capacitance retention after 5000 cycles).

Tuning the electrical properties of graphene oxide through low-temperature thermal annealing

During the last fifteen years, the reduction of electrically insulating graphene oxide (GO) through the elimination of oxygen containing functional groups and the restoration of sp² conjugation yielding its conducting form, known as reduced graphene oxide (rGO), has been widely investigated as a scalable and low-cost method to produce materials featuring graphene-like characteristics. Among various protocols, thermal annealing represents an attractive green approach compatible with industrial processes. However, the high temperatures typically required to accomplish this process are energetically demanding and are incompatible with the use of plastic substrates often desired for flexible electronics applications. Here, we report a systematic study on the low-temperature annealing of GO by optimizing different annealing conditions, i.e., temperature, time, and reduction atmosphere. We show that the reduction is accompanied by structural changes of GO, which affect its electrochemical performance when used as an electrode material in supercapacitors. We demonstrate that thermally-reduced GO (TrGO) obtained under air or inert atmosphere at relatively low temperatures (<300 °C) exhibits low film resistivities (10^-2-10^-4 Ω m) combined with unaltered resistance after 2000 bending cycles when supported on plastic substrates. Moreover, it exhibits enhanced electrochemical characteristics with a specific capacitance of 208 F g^-1 and a capacitance retention of >99% after 2000 cycles. The reported strategy is an important step forward toward the development of environmentally friendly TrGO for future electrical or electrochemical applications.

Supramolecular Engineering of Cathode Materials for Aqueous Zinc-ion Energy Storage Devices: Novel Benzothiadiazole Functionalized Two-Dimensional Olefin-Linked COFs

Two-dimensional covalent organic frameworks (COFs) have emerged as promising materials for energy storage applications exhibiting enhanced electrochemical performance. While most of the reported organic cathode materials for zinc-ion batteries use carbonyl groups as electrochemically-active sites, their high hydrophilicity in aqueous electrolytes represents a critical drawback. Herein, we report a novel and structurally robust olefin-linked COF-TMT-BT synthesized via the aldol condensation between 2,4,6-trimethyl-1,3,5-triazine (TMT) and 4,4'-(benzothiadiazole-4,7-diyl)dibenzaldehyde (BT), where benzothiadiazole units are explored as novel electrochemically-active groups. Our COF-TMT-BT exhibits an outstanding Zn²⁺ storage capability, delivering a state-of-the-art capacity of 283.5 mAh g^-1 at 0.1 A g^-1 . Computational and experimental analyses reveal that the charge-storage mechanism in COF-TMT-BT electrodes is based on the supramolecularly engineered and reversible Zn²⁺ coordination by the benzothiadiazole units.

Novel thiophene-based donor-acceptor scaffolds as cathodes for rechargeable aqueous zinc-ion hybrid supercapacitors

Well-defined π-conjugated thiophene donor-acceptor molecules play an important role in different fields ranging from synthetic chemistry to materials science. Their chemical structure provides specific electronic and physicochemical properties, which can be further tuned by the introduction of functional groups. Herein, we design and synthesize two novel thiophene-based π-conjugated donor-acceptor molecules TDA-1 and TDA-2 through Aldol and Knoevenagel condensations. In our proof-of-concept study we report for the first time on the use of small organic molecules employed in aqueous zinc-ion hybrid supercapacitors (Zn-HSCs),which exhibit capacitance as high as 206.7 and 235.2 F g^-1 for TDA-1, and TDA-2, respectively.

Schiff base capped gold nanoparticles for transition metal cation sensing in organic media

We report a fast and ultrasensitive colorimetric method for the detection of transition metal ions (Fe³⁺, Cu²⁺, Ni²⁺) in a mixture of toluene-acetonitrile using Schiff base functionalized gold nanoparticles. We achieved limits of detection for the three metal ions at least two orders of magnitude lower than the EU recommended limits. Finally, our methodology was assessed for the determination of nickel in the organic waste of a relevant industrial reaction.

Quantum Capacitance through Molecular Infiltration of 7,7,8,8-Tetracyanoquinodimethane in Metal-Organic Framework/Covalent Organic Framework Hybrids

Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have been extensively investigated during the last two decades. More recently, a family of hybrid materials (i.e., MOF@COF) has emerged as particularly appealing for gas separation and storage, catalysis, sensing, and drug delivery. MOF@COF hybrids combine the unique characteristics of both MOF and COF components and exhibit peculiar properties including high porosity and large surface area. In this work, we show that the infiltration of redox-active 7,7,8,8-tetracyanoquinodimethane (TCNQ) molecules into the pores of MOF@COF greatly improves the characteristics of the latter, thereby attaining high-performance energy storage devices. Density functional theory (DFT) calculations were employed to guide the design of a MOF@COF-TCNQ hybrid with the TCNQ functional units incorporated in the pores of MOF@COF. To demonstrate potential application of our hybrids, the as-synthesized MOF@COF-TCNQ hybrid has been employed as an active material in supercapacitors. Electrochemical energy storage analysis revealed outstanding supercapacitor performance, as evidenced by a specific areal capacitance of 78.36 mF cm^-2 and a high stack volumetric energy density of 4.46 F cm^-3, with a capacitance retention of 86.4% after 2000 cycles completed at 0.2 A cm^-2. DFT calculation results strongly indicate that the high capacitance of MOF@COF-TCNQ has a quantum capacitance origin. Our liquid-phase infiltration protocol of MOF@COF hybrids with redox-active molecules represents a efficacious approach to design functional porous hybrids.

Solution-Processed Graphene-Nanographene van der Waals Heterostructures for Photodetectors with Efficient and Ultralong Charge Separation

Sensitization of graphene with inorganic semiconducting nanostructures has been demonstrated as a powerful strategy to boost its optoelectronic performance. However, the limited tunability of optical properties and toxicity of metal cations in the inorganic sensitizers prohibits their widespread applications, and the in-depth understanding of the essential interfacial charge-transfer process within such hybrid systems remains elusive. Here, we design and develop high-quality nanographene (NG) dispersions with a large-scale production using high-shear mixing exfoliation. The physisorption of these NG molecules onto graphene gives rise to the formation of graphene-NG van der Waals heterostructures (VDWHs), characterized by strong interlayer coupling through π-π interactions. As a proof of concept, photodetectors fabricated on the basis of such VDWHs show ultrahigh responsivity up to 4.5 × 10⁷ A/W and a specific detectivity reaching 4.6 × 10¹³ Jones, being competitive with the highest values obtained for graphene-based photodetectors. The outstanding device characteristics are attributed to the efficient transfer of photogenerated holes from NGs to graphene and the long-lived charge separation at graphene-NG interfaces (beyond 1 ns), as elucidated by ultrafast terahertz (THz) spectroscopy. These results demonstrate the great potential of such graphene-NG VDWHs as prototypical building blocks for high-performance, low-toxicity optoelectronics.

Harnessing selectivity in chemical sensing via supramolecular interactions: from functionalization of nanomaterials to device applications

Chemical sensing is a strategic field of science and technology ultimately aiming at improving the quality of our lives and the sustainability of our Planet. Sensors bear a direct societal impact on well-being, which includes the quality and composition of the air we breathe, the water we drink, and the food we eat. Pristine low-dimensional materials are widely exploited as highly sensitive elements in chemical sensors, although they suffer from lack of intrinsic selectivity towards specific analytes. Here, we showcase the most recent strategies on the use of (supra)molecular interactions to harness the selectivity of suitably functionalized 0D, 1D, and 2D low-dimensional materials for chemical sensing. We discuss how the design and selection of receptors via machine learning and artificial intelligence hold a disruptive potential in chemical sensing, where selectivity is achieved by the design and high-throughput screening of large libraries of molecules exhibiting a set of affinity parameters that dictates the analyte specificity. We also discuss the importance of achieving selectivity along with other relevant characteristics in chemical sensing, such as high sensitivity, response speed, and reversibility, as milestones for true practical applications. Finally, for each distinct class of low-dimensional material, we present the most suitable functionalization strategies for their incorporation into efficient transducers for chemical sensing.

Self-Assembly of Functionalized Lipophilic Guanosines into Cation-Free Stacked Guanine-Quartets

The hierarchical self-assembly of various lipophilic guanosines exposing either a phenyl or a ferrocenyl group in the C(8) position was investigated. In a solution, all the derivatives were found to self-assemble primarily into isolated guanine (G)-quartets. In spite of the apparent similar bulkiness of the two substituents, most of the derivatives form disordered structures in the solid state, whereas a specific 8-phenyl derivative self-assembles into an unprecedented, cation-free stacked G-quartet architecture.

Chemical Conversion and Locking of the Imine Linkage: Enhancing the Functionality of Covalent Organic Frameworks

Imine-based covalent organic frameworks (COFs) are a widely studied class of functional, crystalline, and porous nanostructures which combine a relatively facile crystallization with tuneable compositions and porosities. However, the imine linkage constitutes an intrinsic limitation due to its reduced stability in harsh chemical conditions and its unsuitability for in-plane π-conjugation in COFs. Urgent solutions are therefore required in order to exploit the full potential of these materials, thereby enabling their technological application in electronics, sensing, and energy storage devices. In this context, the advent of a new generation of linkages derived from the chemical conversion and locking of the imine bond represents a cornerstone for the synthesis of new COFs. A marked increase in the framework robustness is in fact often combined with the incorporation of novel functionalities including, for some of these reactions, an extension of the in-plane π-conjugation. This Minireview describes the most enlightening examples of one-pot reactions and post-synthetic modifications towards the chemical locking of the imine bond in COFs.

High-sorption terpyridine-graphene oxide hybrid for the efficient removal of heavy metal ions from wastewater

Pollution of wastewater with heavy metal-ions represents one of the most severe environmental problems associated with societal development. To overcome this issue, the design of new, highly efficient systems capable of removing such toxic species, hence to purify water, is of paramount importance for public health and environmental protection. In this work, novel sorption hybrid materials were developed to enable high-performance adsorption of heavy metal ions. Towards this end, graphene oxide (GO) exhibiting various C/O ratios has been functionalized with ad hoc receptors, i.e. terpyridine ligands. The maximum adsorption capacity of highly oxidized/terpyridine hybrids towards Ni(ii), Zn(ii) and Co(ii) was achieved at pH = 6 and 25 °C reaching values of 462, 421 and 336 mg g-1, respectively, being the highest reported in the literature for pristine GO and GO-based sorbents. Moreover, the uptake experiments showed that heavy metal ion adsorption on GO-Tpy and GOh-Tpy is strongly dependent on pH in the range from 2 to 10, as a result of the modulation of interactions at the supramolecular level. Moreover, the ionic strength was found to be independent of heavy metal ion adsorption on GO-Tpy and GOh-Tpy. Under ambient conditions, adsorption capacity values increase with the degree of oxidation of GO because dipolar oxygen units can both interact with heavy-metal ions via dipole-dipole and/or ionic interactions and enable bonding of more covalently anchored terpyridine units. Both adsorption isotherms and kinetics studies revealed that the uptake of the heavy metal ions occurs at a monolayer coverage, mostly controlled by the strong surface complexation with the oxygen of GO and nitrogen-containing groups of terpyridine. Furthermore, selectivity of the hybrid was confirmed by selective sorption of the above heavy metal ions from mixtures involving alkali (Na(i), K(i)) and alkaline Earth (Mg(ii), Ca(ii)) metal ions due to the chelating properties of the terpyridine subunits, as demonstrated with municipal drinking (tap) water samples. Our findings provide unambiguous evidence for the potential of chemical tailoring of GO-based materials with N-heterocyclic ligands as sorbent materials for highly efficient wastewater purification.

Electrochemically Exfoliated Graphene for High-Durability Cement Composites

The development of radically new types of corrosion-resistant cement composites is nowadays compulsory in view of the continuous increase of concrete consumption combined with the intrinsically defective nature of concrete. Among various additives being employed in the concrete technology, carbon nanomaterials have emerged as extremely powerful components capable of remarkably enhancing nano- and microstructures as well as properties of cement-based composites. In this study, we demonstrate that cement mortar incorporating electrochemically exfoliated graphene (EEG) exhibits significantly improved fluid transport properties. The addition of 0.05 wt % of EEG to ordinary Portland cement mortar results in the reduction of initial and secondary sorptivity values by 21 and 25%, respectively. This leads to the outstanding resistance of EEG-cement composites to highly corrosive environments, namely, chloride and sulfate solutions. These observations, combined with the previously reported remarkable enhancement of the tensile strength of EEG-cement mortars, represent a major step toward the development of highly durable graphene-based cement composites.

2D MXene-Molecular Hybrid Additive for High-Performance Ambipolar Polymer Field-Effect Transistors and Logic Gates

MXenes are highly conductive layered materials that are attracting a great interest for high-performance opto-electronics, photonics, and energy applications.. Their non-covalent functionalization with ad hoc molecules enables the production of stable inks of 2D flakes to be processed in thin-films. Here, the formation of stable dispersions via the intercalation of Ti₃ C₂ T_x with didecyldimethyl ammonium bromide (DDAB) yielding Ti₃ C₂ T_x -DDAB, is demonstrated. Such functionalization modulates the properties of Ti₃ C₂ T_x , as evidenced by a 0.47 eV decrease of the work function. It is also shown that DDAB is a powerful n-dopant capable of enhancing electron mobility in conjugated polymers and 2D materials. When Ti₃ C₂ T_x -DDAB is blended with poly(diketopyrrolopyrrole-co-selenophene) [(PDPP-Se)], a simultaneous increase by 170% and 152% of the hole and electron field-effect mobilities, respectively, is observed, compared to the neat conjugated polymer, with values reaching 2.0 cm² V^-1 s^-1 . By exploiting the balanced ambipolar transport of the Ti₃ C₂ T_x -DDAB/PDPP-Se hybrid, complementary metal-oxide-semiconductor (CMOS) logic gates are fabricated that display well-centered trip points and good noise margin (64.6% for inverter). The results demonstrate that intercalant engineering represents an efficient strategy to tune the electronic properties of Ti₃ C₂ T_x yielding functionalized MXenes for polymer transistors with unprecedented performances and functions.

Functionalized 4,4'-Bipyridines: Synthesis and 2D Organization on Highly Oriented Pyrolytic Graphite

Commercial 4,4'-bipyridine is a popular scaffold that is primarily employed as a linker in 3D self-assembled architectures such as metallo-organic frameworks or as a connector in 2D networks. The introduction of alkyl substituents on the bipyridine skeleton is instrumental when 4,4'-bipyridines are used as linkers to form 2D self-assembled patterns on surfaces. Here, several synthetic strategies to access 4,4'-bipyridines functionalized at various positions are described. These easily scalable reactions have been used to introduce a range of alkyl substituents at positions 2 and 2' or 3 and 3' and at positions 2,2' and 6,6' in the case of tetra-functionalization. Scanning tunneling microscopy studies of molecular monolayers physisorbed at the graphite-solution interface revealed different supramolecular patterns whose motifs are primarily dictated by the nature and position of the alkyl chains.

Highly Sensitive Strain Sensors Based on Molecules-Gold Nanoparticles Networks for High-Resolution Human Pulse Analysis

High-performance flexible strain sensors are key components for the next generation of wearable health monitoring devices. Here, the authors have fabricated a novel strain sensor based on gold nanoparticles (AuNPs) interconnected by flexible and responsive molecular linkers. The combination of conductive AuNPs (25 nm in diameter) with tetra(ethylene glycol) dithiol (SH-TEG-SH) linkers yields a covalent 3D network which can be directly deposited onto prepatterned flexible supports exposing interdigitated Au electrodes. The electrically insulating nature of the linkers effectively defines the tunneling modulated charge transfer through the AuNPs network. When compressive/tensile strain is applied, the molecular linkers adopt a compressed/stretched conformation thus decreasing/increasing the interparticle distance, ultimately yielding an exponential increase/decrease of the tunneling current when voltage is applied. The strain sensor displays state-of-the-art performances including a highly sensitive response to both tensile and compressive strain, as quantified by a high gauge factor (GF≈126) combined with other superior sensing properties like high flexibility, short response time (16.1 ms), and good robustness (>2000 cycles). Finally, the applicability of the device for health monitoring is demonstrated: high-resolution artery pulse waves are acquired by placing the strain sensor onto the skin allowing the extraction of important physical parameters for human-health assessment.

Effect of temperature and exfoliation time on the properties of chemically exfoliated MoS2 nanosheets

A systematic investigation of the experimental conditions for the chemical exfoliation of MoS₂ using n-butyllithium as intercalating agent has been carried out to unravel the effect of reaction time and temperature for maximizing the percentage of monolayer thick-flakes and achieve a control over the content of metallic 1T vs. semiconductive 2H phases, thereby tuning the electrical properties of ultrathin MoS₂ few-layer thick films.

His-bundle pacing in CHF-patients with narrow QRS and chronic AF – an upgrade from single-chamber to dual-chamber ICD

 

A single-chamber ICD is a standard method for primary SCD prophylaxis. In patients with chronic atrial fibrillation it does not contribute to the regularization of heart rate, which is crucial for proper treatment. Moreover, to avoid the deleterious effect of right ventricular pacing only minority of the patients with single chamber ICD get the appropriate, recommended dose of beta-blockers.

The aim of our study was to assess the efficacy of direct His-bundle pacing in a population of patients with congestive heart failure and chronic atrial fibrillation using upgrade from single chamber to dual-chamber ICD and atrial channel to perform the His-bundle pacing

Methods

The study population included 39 patients (37 men, 2 women) aged 67.2±9.3 years, with CHF and chronic AF implanted primarily with single chamber ICD with established pharmacotherapy and stable clinical status.

Results

The echocardiography measurements at baseline and during follow-up were presented in the table:

During short period (3–6 months) of follow-up the mean values of EF and LV dimensions significantly improved. This was also accompanied by functional status improvement.

Conclusions

His-bundle-based pacing in CHF-chronic AF patients contributes to significant echocardiographic and clinical improvement. Standard single-chamber ICD implantation in CHF-chronic AF patients yields only SCD prevention without influence on remodeling process. The physiological pacing contributes to better pharmacotherapy.

Funding Acknowledgement

Type of funding source: None

Atrial and atrioventricular resynchronization the benefit of bachmanns bundle and his bundle pacing

 

The current treatment of patients with heart failure and concomitant atrioventricular conduction delay is difficult. Recommendations indicate the possibility to use the classic resynchronization but in the presence of narrow QRS-complex such approach could be even harmful. Without a sufficient LBBB morphology as indication for classical CRT, those patients would lose their narrow QRS complex with negative consequences for the hearts functional status.

A new therapeutic option for those patients to re-establish the physiological atrioventricular mechanical sequence is the permanent His-bundle pacing (pHBP). Advantages like physiological activation sequence of the ventricular myocardium, less affected by AF compared to classical CRT and reversal of mitral regurgitation should be enumerated to show it's beneficial effect. Additionally the use of Bachmann's-bundle pacing can correct the prolonged interatrial conduction thus further contribute to the echocardiographic and clinical improvement.

The aim of the study is to assess the influence of Bachmann's-bundle pacing and His-bundle pacing on the reversed remodeling of the heart in patients with heart failure and atrioventricular block.

The study group included 21 patients (7 women and 14 men) undergoing cardiac resynchronization using Bachmann's-bundle pacing and permanent His-bundle pacing from LV channel for atrioventricular conduction delay. All the patients had narrow QRS-complex which prevented us to use classic resynchronization. 13 CRT-D and 8 CRT-P devices were implanted according to the ejection fraction and ventricular arrhythmia risk assessment. In all patients the direct His-bundle pacing was successfully achieved, selective in 17 and non-selective in 4 patients. The mean follow-up (FU) period was 8.8 months (1–26 months). The echocardiographic, clinical and ECG results are presented in the table 1.

Conclusions

1. The correction of atrioventricular and interatrial conduction delay resulting in improvement of atrioventricular mechanical coupling can contribute to the reversed remodeling of the heart.

2. This also improves the patient's functional status.

3. In some patients this approach could lead to the normalization of echocardiographic parameters of the left ventricle.

Funding Acknowledgement

Type of funding source: None

Ultrafast and Highly Sensitive Chemically Functionalized Graphene Oxide-Based Humidity Sensors: Harnessing Device Performances via the Supramolecular Approach

Humidity sensors have been gaining increasing attention because of their relevance for well-being. To meet the ever-growing demand for new cost-efficient materials with superior performances, graphene oxide (GO)-based relative humidity sensors have emerged recently as low-cost and highly sensitive devices. However, current GO-based sensors suffer from important drawbacks including slow response and recovery, as well as poor stability. Interestingly, reduced GO (rGO) exhibits higher stability, yet accompanied by a lower sensitivity to humidity due to its hydrophobic nature. With the aim of improving the sensing performances of rGO, here we report on a novel generation of humidity sensors based on a simple chemical modification of rGO with hydrophilic moieties, i.e., triethylene glycol chains. Such a hybrid material exhibits an outstandingly improved sensing performance compared to pristine rGO such as high sensitivity (31% increase in electrical resistance when humidity is shifted from 2 to 97%), an ultrafast response (25 ms) and recovery in the subsecond timescale, low hysteresis (1.1%), excellent repeatability and stability, as well as high selectivity toward moisture. Such highest-key-performance indicators demonstrate the full potential of two-dimensional (2D) materials when decorated with suitably designed supramolecular receptors to develop the next generation of chemical sensors of any analyte of interest.

Reduced graphene oxide-silsesquioxane hybrid as a novel supercapacitor electrode

Supercapacitor energy storage devices recently garnered considerable attention due to their cost-effectiveness, eco-friendly nature, high power density, moderate energy density, and long-term cycling stability. Such figures of merit render supercapacitors unique energy sources to power portable electronic devices. Among various energy storage materials, graphene-related materials have established themselves as ideal electrodes for the development of elite supercapacitors because of their excellent electrical conductivity, high surface area, outstanding mechanical properties combined with the possibility to tailor various physical and chemical properties via chemical functionalization. Increasing the surface area is a powerful strategy to improve the performance of supercapacitors. Here, modified polyhedral oligosilsesquioxane (POSS) is used to improve the electrochemical performance of reduced graphene oxide (rGO) through the enhancement of porosity and the extension of interlayer space between the sheets allowing efficient electrolyte transport. rGO-POSS hybrids exhibited a high specific capacitance of 174 F g^-1, power density reaching 2.25 W cm^-3, and high energy density of 41.4 mW h cm^-3 endowed by the introduction of POSS spacers. Moreover, these electrode materials display excellent durability reaching >98% retention after 5000 cycles.

On the rapid in situ oxidation of two-dimensional V2CTz MXene in culture cell media and their cytotoxicity

The plethora of emerging two-dimensional (2D) materials exhibit wide potential application in novel technologies and advanced devices. However, their stability in environmental conditions could be an issue, affecting their application possibilities and posing health risks. Moreover, their decomposed leftovers can also induce a negative influence on human health. In particular, transition metal carbides commonly referred to as MXenes are susceptible to environmental oxidation being decomposed toward transition metal oxides and carbide-derived carbon. In this study we focused on the oxidation-state-related in vitro cytotoxicity of delaminated V₂CT_z onto immortalized keratinocytes (HaCaT) and malignant melanoma (A375) human cell lines. Due to the fact, that the V₂CT_x MXenes are least stable from all known obtained MXenes up to date, the vanadium ones were a practical choice to visualize the oxidation-cytotoxic correlation keeping the standards of 24-48 h of cell culturing. We found that the oxidation of V₂CT_z highly increases their cytotoxicity toward human cells, which is also time and dose dependent. The identified mode of action relates to the cell cycle as well as cellular membrane disintegration through direct physicochemical interactions.

Synthesis of Robust MOFs@COFs Porous Hybrid Materials via an Aza-Diels-Alder Reaction: Towards High-Performance Supercapacitor Materials

Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have attracted enormous attention in recent years. Recently, MOF@COF are emerging as hybrid architectures combining the unique features of the individual components to enable the generation of materials displaying novel physicochemical properties. Herein we report an unprecedented use of aza-Diels-Alder cycloaddition reaction as post-synthetic modification of MOF@COF-LZU1, to generate aza-MOFs@COFs hybrid porous materials with extended π-delocalization. A a proof-of-concept, the obtained aza-MOFs@COFs is used as electrode in supercapacitors displaying specific capacitance of 20.35 μF cm^-2 and high volumetric energy density of 1.16 F cm^-3 . Our approach of post-synthetic modification of MOFs@COFs hybrids implement rational design for the synthesis of functional porous materials and expands the plethora of promising application of MOFs@COFs hybrid porous materials in energy storage applications.

Photomodulation of Charge Transport in All-Semiconducting 2D-1D van der Waals Heterostructures with Suppressed Persistent Photoconductivity Effect

Van der Waals heterostructures (VDWHs), obtained via the controlled assembly of 2D atomically thin crystals, exhibit unique physicochemical properties, rendering them prototypical building blocks to explore new physics and for applications in optoelectronics. As the emerging alternatives to graphene, monolayer transition metal dichalcogenides and bottom-up synthesized graphene nanoribbons (GNRs) are promising candidates for overcoming the shortcomings of graphene, such as the absence of a bandgap in its electronic structure, which is essential in optoelectronics. Herein, VDWHs comprising GNRs onto monolayer MoS₂ are fabricated. Field-effect transistors (FETs) based on such VDWHs show an efficient suppression of the persistent photoconductivity typical of MoS₂ , resulting from the interfacial charge transfer process. The MoS₂ -GNR FETs exhibit drastically reduced hysteresis and more stable behavior in the transfer characteristics, which is a prerequisite for the further photomodulation of charge transport behavior within the MoS₂ -GNR VDWHs. The physisorption of photochromic molecules onto the MoS₂ -GNR VDWHs enables reversible light-driven control over charge transport. In particular, the drain current of the MoS₂ -GNR FET can be photomodulated by 52%, without displaying significant fatigue over at least 10 cycles. Moreover, four distinguishable output current levels can be achieved, demonstrating the great potential of MoS₂ -GNR VDWHs for multilevel memory devices.

Molecular Springs: Integration of Complex Dynamic Architectures into Functional Devices

Molecular/supramolecular springs are artificial nanoscale objects possessing well-defined structures and tunable physicochemical properties. Like a macroscopic spring, supramolecular springs are capable of switching their nanoscale conformation as a response to external stimuli by undergoing mechanical spring-like motions. This dynamic action offers intriguing opportunities for engineering molecular nanomachines by translating the stimuli-responsive nanoscopic motions into macroscopic work. These nanoscopic objects are reversible dynamic multifunctional architectures which can express a variety of novel properties and behave as adaptive nanoscopic systems. In this Minireview, we focus on the design and structure-property relationships of supramolecular springs and their (self-)assembly as a prerequisite towards the generation of novel dynamic materials featuring controlled movements to be readily integrated into macroscopic devices for applications in sensing, robotics, and the internet of things.

Enhancement of Charge Transport in Polythiophene Semiconducting Polymer by Blending with Graphene Nanoparticles

This paper describes a study on the charge transport in a composite of liquid-exfoliated graphene nanoparticles (GNPs) and a polythiophene semiconducting polymer. While the former component is highly conducting, although it consists of isolated nanostructures, the latter offers an efficient charge transport path between the individual GNPs within the film, overall yielding enhanced charge transport properties of the resulting bi-component system. The electrical characteristics of the composite layers were investigated by means of measurements of time-of-flight photoconductivity and transconductance in field-effect transistors. In order to analyze both phenomena separately, charge density and charge mobility contributions to the conductivity were singled out. With the increasing GNP concentration, the charge mobility was found to increase, thereby reducing the time spent by the carriers on the polymer chains. In addition, for GNP loading above 0.2 % (wt.), an increase of free charge density was observed that highlights an additional key role played by doping. Variable-range hopping model of a mixed two- and three-dimensional transport is explained using temperature dependence of mobility and free charge density. The temperature variation of free charge density was related to the electron transfer from polythiophene to GNP, with an energy barrier of 24 meV.

Simultaneous non-covalent bi-functionalization of 1T-MoS2 ruled by electrostatic interactions: towards multi-responsive materials

Dual functionalization of chemically exfoliated MoS₂ has been achieved by exploiting coulombic interactions among positively charged molecules and the negatively charged 2D flakes.

P1239His-bundle pacing in CHF-patients with narrow QRS and chronic AF using dual-chamber ICD

Methods

The study population included 78 patients with CHF and chronic AF: group A - 56 pts treated with direct His-bundle pacing using atrial port of dual chamber ICD and group B - 22 patients implanted with single chamber ICD as recommended by the guidelines. The patients in group B constituting clinical controls were derived from the Heart Failure Outpatients Clinic with established clinical status and pharmacotherapy.

Results

The demographic data, clinical characteristics and echocardiography measurements at baseline and during follow-up were presented in the table:

Table 1 Group A Group B P value Age (years) 69.7±6.9 66.7±11.3 n.s. Sex (% of male sex) 84.0 86.4 n.s. Ventricular pacing (%) – 46.3±31.2 – His-bundle pacing (%) 81.7±9.2 – – pre post pre post pre vs. post LVEDD (mm) 66.9±4.9 59.9±4.7 64.8±8.0 64.7±8.1 <0.01 n.s. EF (%) 29.6±3.8 43.6±5.9 28.1±6.1 28.8±7.3 <0.01 n.s. NYHA class 2.7±0.6 1.4±0.6 2.5±0.6 2.0±0.2 <0.05 n.s. B-blocker dose (metoprolol equivalent dose) 104.6±41.6 214.3±82.6 78.3±56.6 103.1±49.2 <0.001 <0.05

During 12-months of follow-up the mean values of NYHA functional class, EF and LV dimensions did not change in group B but significantly improved in group A. The physiological His-bundle based pacing enabled optimal beta-blocker dosing. The studied groups had no tachyarrhythmia at baseline so the presumable atrial fibrillation-related harm depends on the rhythm irregularity.

Conclusions

His-bundle-based pacing in CHF-chronic AF patients contributes to significant echocardiographic and clinical improvement. Standard single-chamber ICD implantation in CHF-chronic AF patients yields only SCD prevention without influence on remodeling process. The CHF-patients with narrow QRS and chronic AF benefit from substantially higher beta-blockade which can be instituted in His-bundle pacing group.

P5426His-bundle pacing in CHF-patients with narrow QRS and chronic AF using dual-chamber ICD - an upgrade from single-chamber to dual-chamber ICD

Methods

The study population included 21 patients with CHF and chronic AF implanted primarily with single chamber ICD with etablished pharmacotherapy and stable clinical status.

Results

The echocardiography measurements at baseline and during ollow-up were presented in the table:

Table 1 Baseline Follow-up p-value LVEDD (ms) 67.7±10.7 64.5±8.6 <0.05 EF (%) 27.0±4.8 33.2±6.9 <0.05 NYHA class 2.8±0.6 1.9±0,5 <0.05

During short 4-months of follow-up the mean values of EF and LV dimensions significantly improved. This was also accompanied by functional status improvement.

Conclusions

His-bundle-based pacing in CHF-chronic AF patients contributes to significant echocardiographic and clinical improvement. Standard single-chamber ICD implantation in CHF-chronic AF patients yields only SCD prevention without influence on remodeling process.

Water-Dispersed High-Quality Graphene: A Green Solution for Efficient Energy Storage Applications

Graphene has been the subject of widespread research during the past decade because of its outstanding physical properties which make it an ideal nanoscale material to investigate fundamental properties. Such characteristics promote graphene as a functional material for the emergence of disruptive technologies. However, to impact daily life products and devices, high-quality graphene needs to be produced in large quantities using an environmentally friendly protocol. In this context, the production of graphene which preserves its outstanding electronic properties using a green chemistry approach remains a key challenge. Herein, we report the efficient production of electrode material for micro-supercapacitors obtained by functionalization of water-dispersed high-quality graphene nanosheets with polydopamine. High-frequency (terahertz) conductivity measurements of the graphene nanosheets reveal high charge carrier mobility up to 1000 cm^-2 V^-1 s^-1. The fine water dispersibility enables versatile functionalization of graphene, as demonstrated by the pseudocapacitive polydopamine coating of graphene nanosheets. The polydopamine functionalization causes a modest, i.e., 20%, reduction of charge carrier mobility. Thin film electrodes based on such hybrid materials for micro-supercapacitors exhibit excellent electrochemical performance, namely a volumetric capacitance of 340 F cm^-3 and a power density of 1000 W cm^-3, thus outperforming most of the reported graphene-based micro-supercapacitors. These results highlight the potential for water-dispersed, high-quality graphene nanosheets as a platform material for energy-storage applications.

High-Performance Graphene-Based Cementitious Composites

This study reports on the development of a cementitious composite incorporating electrochemically exfoliated graphene (EEG). This hybrid functional material features significantly enhanced microstructure and mechanical properties, as well as unaffected workability; thus, it outperforms previously reported cementitious composites containing graphene derivatives. The manufacturing of the composite relies on a simple and efficient method that enables the uniform dispersion of EEG within cement matrix in the absence of surfactants. Different from graphene oxide, EEG is found to not agglomerate in cement alkaline environment, thereby not affecting the fluidity of cementitious composites. The addition of 0.05 wt% graphene content to ordinary Portland cement results in an increase up to 79%, 8%, and 9% for the tensile strength, compressive strength, and Young's modulus, respectively. Remarkably, it is found that the addition of EEG promotes the hydration reaction of both alite and belite, thus leading to the formation of a large fraction of 3CaO·2SiO2·3H2O (C-S-H) phase. These findings represent a major step forward toward the practical application of nanomaterials in civil engineering.

Molecule-Graphene Hybrid Materials with Tunable Mechanoresponse: Highly Sensitive Pressure Sensors for Health Monitoring

The development of pressure sensors is crucial for the implementation of electronic skins and for health monitoring integrated into novel wearable devices. Tremendous effort is devoted toward improving their sensitivity, e.g., by employing microstructured electrodes or active materials through cumbersome processes. Here, a radically new type of piezoresistive pressure sensor based on a millefeuille-like architecture of reduced graphene oxide (rGO) intercalated by covalently tethered molecular pillars holding on-demand mechanical properties are fabricated. By applying a tiny pressure to the multilayer structure, the electron tunnelling ruling the charge transport between successive rGO sheets yields a colossal decrease in the material's electrical resistance. Significantly, the intrinsic rigidity of the molecular pillars employed enables the fine-tuning of the sensor's sensitivity, reaching sensitivities as high as 0.82 kPa^-1 in the low pressure region (0-0.6 kPa), with short response times (≈24 ms) and detection limit (7 Pa). The pressure sensors enable efficient heartbeat monitoring and can be easily transformed into a matrix capable of providing a 3D map of the pressure exerted by different objects.

Persian waxing of graphite: towards green large-scale production of graphene

Large quantities of high-quality graphene has been produced through a green and up-scalable method based on the exfoliation and dispersion of graphene in a sugar-based wax, by mimicking the Scotch tape approach to enable the production of graphene paste with unprecedently high concentration of 30% in weight exhibiting ultrahigh stability.

Tailoring the physicochemical properties of solution-processed transition metal dichalcogenides via molecular approaches

In this Feature Article we highlight the tremendous progress in solution-processed transition metal dichalcogenides and the molecular approaches employed to finely tune their physicochemical properties.