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Copper and silver nanowires as novel electrocatalysts for the electroreduction of CO2.

We describe, for a single platinum complex bearing a dipeptide moiety, a solvent-driven interconversion from twisted to straight micrometric assembled structures with different chirality. The photophysical and morphological properties of the aggregates have been investigated as well as the role of the media and concentration. A real-time visualization of the solvent-driven interconversion processes has been achieved by confocal microscopy. Finally, atomistic and coarse-grained simulations, providing results consistent with the experimental observations, allow to obtain a molecular-level insight into the interesting solvent-responsive behavior of this system., Visualizing the interconversion from chiral helices to ribbons like-structures of self-assembled luminescent platinum complexes.

Abstract The discovery of aggregation-induced electrochemiluminescence (AIECL) in 2017 opened new research paths in the quest for novel, more efficient emitters and platforms for biological and environmental sensing applications. The great abundance of fluorophores presenting aggregation-induced emission in aqueous media renders AIECL a potentially powerful tool for future diagnostics. In the short time following this discovery, many scientists have found the phenomenon interesting, with research findings contributing to advances in the comprehension of the processes involved and in attempts to design new sensing platforms. Herein, we explore these advances and reflect on the future directions to take for the development of sensing devices based on AIECL. Graphic abstract

The discovery of aggregation-induced electrochemiluminescence (AIECL) in 2017 opened new research paths in the quest for novel, more efficient emitters and platforms for biological and environmental sensing applications. The great abundance of fluorophores presenting aggregation-induced emission in aqueous media renders AIECL a potentially powerful tool for future diagnostics. In the short time following this discovery, many scientists have found the phenomenon interesting, with research findings contributing to advances in the comprehension of the processes involved and in attempts to design new sensing platforms. Herein, we explore these advances and reflect on the future directions to take for the development of sensing devices based on AIECL.

We report the synthesis of ultralong copper sulfide nanowires (Cu2−xSNWs) through the sulphidation reaction of metallic copper nanowires (CuNWs) by thiourea under mild conditions. The multiscale characterization of Cu2−xSNWs revealed the presence of a core shell structure made up of an external covellite layer coating a roxbyite core. The Cu2−xSNWs, exhibiting lengths as high as 200 μm, can be easily dispersed in ethanol and deposited onto arbitrary substrates such as glass or plastic. The resulting films are readily conducting without the need for post-treatments and exhibit a sheet resistance of 4.1 kΩ sq−1 at 73.7% transmittance (at 550 nm), by virtue of the high aspect ratio of the Cu2−xSNWs. The multiscale electrical characterization down to the single Cu2−xSNWs revealed a low resistivity of 6.9 × 10−6 Ω m and perfect Ohmic conductivity. Interestingly, the conductivity of Cu2−xSNW films supported on polyethylene naphthalate sheets remained almost unaltered (4% decrease) after 10 000 bending cycles. In addition, Cu2−xSNWs have shown excellent chemical stability towards a strong oxidant like FeCl3 as well as in an acidic environment. Finally, Cu2−xSNWs have been employed as active materials in symmetric supercapacitors revealing good pseudocapacitive behaviour, with specific capacity as high as 324 F g−1 (at 5 mV s−1) and 70% retention of the initial capacitance after 5000 cycles (at 100 mV s−1).

An important aspect in the field of supramolecular chemistry is the control of the composition and aggregation state of supramolecular polymers and the possibility of stabilizing out-of-equilibrium states. The ability to freeze metastable systems and release them on demand, under spatiotemporal control, to allow their thermodynamic evolution toward the most stable species is a very attractive concept. Such temporal blockage could be realized using stimuli-responsive "boxes" able to trap and redirect supramolecular polymers. In this work, we report the use of a redox responsive nanocontainer, an organosilica nanocage (OSCs), for controlling the dynamic self-assembly pathway of supramolecular aggregates of a luminescent platinum compound (PtAC). The aggregation of the complexes leads to different photoluminescent properties that allow visualization of the different assemblies and their evolution. We discovered that the nanocontainers can encapsulate kinetically trapped species characterized by an orange emission, preventing their evolution into the thermodynamically stable aggregation state characterized by blue-emitting fibers. Interestingly, the out-of-equilibrium trapped Pt species (PtAC@OSCs) can be released on demand by the redox-triggered degradation of OSCs, re-establishing their self-assembly toward the thermodynamically stable state. To demonstrate that control of the self-assembly pathway occurs also in complex media, we followed the evolution of the supramolecular aggregates inside living cells, where the destruction of the cages allows the intracellular release of PtAC aggregates, followed by the formation of microscopic blue emitting fibers. Our approach highlights the importance of "ondemand" confinement as a tool to temporally stabilize transient species which modulate complex self-assembly pathways in supramolecular polymerization.

Self‐assembly relies on the ability of smaller and discrete entities to spontaneously arrange into more organized systems by means of the structure‐encoded information. Herein, we show that the design of the media can play a role even more important than the chemical design. The media not only determines the self‐assembly pathway at a single‐component level, but in a very narrow solvent composition, a supramolecular homo‐aggregate can be non‐covalently wrapped by a second component that possesses a different crystal lattice. Such a process has been followed in real time by confocal microscopy thanks to the different emission colors of the aggregates formed by two isolated PtII complexes. This coating is reversible and controlled by the media composition. Single‐crystal X‐ray diffraction and molecular simulations based on coarse‐grained (CG) models allowed the understanding of the properties displayed by the different aggregates. Such findings could result in a new method to construct hierarchical supramolecular structures., Taking advantage of the useful emitting features of two platinum complexes, we show how the media regulates the assembly pathways from self‐sorting to an unprecedented reversible, dynamic molecular wrapping of a complex on another assembled structure.

We report the electrochemiluminescence properties of square-planar Pt(II) complexes that result from the formation of supramolecular nanostructures. We define this new phenomenon as aggregation-induced electrochemiluminescence (AIECL). In this system, self-assembly changes the HOMO and LUMO energies, making their population accessible via ECL pathways and leading to the generation of the luminescent excited state. Significantly, the emission from the self-assembled system is the first example of electrochemiluminescence (ECL) of Pt(II) complexes in aqueous solution having higher efficiency than the standard, Ru(bpy)32+.The finding can lead to a new generation of bright emitters that can be used as ECL labels.

The self‐assembly of platinum complexes is a well‐documented process that leads to interesting changes of the photophysical and electrochemical behavior as well as to a change in reactivity of the complexes. However, it is still not clear how many metal units must interact in order to achieve the desired properties of a large assembly. This work aimed to clarify the role of the number of interacting PtII units leading to an enhancement of the spectroscopic properties and how to address inter‐ versus intramolecular processes. Therefore, a series of neutral multinuclear PtII complexes were synthesized and characterized, and their photophysical properties at different concentration were studied. Going from the monomer to dimers, the growth of a new emission band and the enhancement of the emission properties were observed. Upon increasing the platinum units up to three, the monomeric blue emission could not be detected anymore and a concentration independent bright‐yellow/orange emission, due to the establishment of intramolecular metallophilic interactions, was observed., Three is better than two: Multinuclear PtII complexes provide valuable insight into the formation of closed shell Pt⋅⋅⋅Pt metallophilic interactions and into the corresponding MMLCT excited state. Persistent aggregation‐induced emission, which is independent from the media, is observed for the trinuclear species, demonstrating that three is better than two.

A Pt(II) complex, bearing an oligo-ethyleneoxide pendant, is able to self-assemble in ultralong ribbons that display mechanochromism upon nanoscale mechanical stimuli, delivered through atomic force microscopy (AFM). Such observation paves the way to fine understanding and manipulation of the mechanochromic properties of such material at the nanoscale. AFM allows quantitative assessment of nanoscale mechanochromism as arising from static pressure (piezochromism) and from shear-based mechanical stimuli (tribochromism), and to compare them with bulk pressure-dependent luminescence observed with diamond-anvil cell (DAC) technique. Confocal spectral imaging reveals that mechanochromism only takes place within short distance from the localized mechanical stimulation, which allows to design high-density information writing with AFM nanolithography applied on individual self-assembled ribbons. Each ribbon hence serves as an individual microsystem for data storage. The orange luminescence of written information displays high contrast compared to cyan native luminescence; moreover, it can be selectively excited with visible light. In addition, ribbons show photochromism, i.e., the emission spectrum changes upon exposure to light, in a similar way as upon mechanical stress. Photochromism is here conveniently used to conceal and eventually erase information previously written with nanolithography by irradiation.

A new technique for direct patterning of functional organic polymers using commercial photolithography setups with a minimal loss of the materials' performances is reported. This result is achieved through novel cross-link agents made by boron- and fluorine-containing heterocycles that can react between themselves upon UV- and white-light exposure.

This chapter addresses the main principles, challenges and achievements in ECL using metal complexes. Selected applications in diagnostics and biosensing are described.

International audience; 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.

During the last decade, two-dimensional materials (2DMs) have attracted great attention due to their unique chemical and physical properties, which make them appealing platforms for diverse applications in opto-electronic devices, energy generation and storage, and sensing. Among their various extraordinary properties, 2DMs possess high surface area-to-volume ratios and ultra-high surface sensitivity to the environment, which are key characteristics for applications in chemical sensing. Furthermore, 2DMs’ superior electrical and optical properties, combined with their excellent mechanical characteristics such as robustness and flexibility, make these materials ideal components for the fabrication of a new generation of high-performance chemical sensors. Depending on the specific device, 2DMs can be tailored to interact with various chemical species at the non-covalent level, making them powerful platforms for fabricating devices exhibiting a high sensitivity towards detection of various analytes including gases, ions and small biomolecules. Here, we will review the most enlightening recent advances in the field of chemical sensors based on atomically-thin 2DMs and we will discuss the opportunities and the challenges towards the realization of novel hybrid materials and sensing devices.

Highly porous foams based on graphene oxide functionalized with polyethylenimine are generated and used with unprecedented efficiency for adsorbing heavy metal ions. A multiscale analysis of the GO–BPEI nanocomposite provided evidence for the covalent grafting of BPEI on GO and the formation of low crystalline porous foams. The uptake experiments revealed that the GO–BPEI's adsorption of toxic cations is strongly dependent on the pH in range from 2 to 10, as a result of the different interactions at the supramolecular level between the metal ions and the GO–BPEI foam. The maximum uptake capacities for Cu(II), Cd(II) and Pb(II) are achieved at pH = 5 and exhibit values as high as 1096, 2051 and 3390 mg g−1, respectively, being ca. over 20 times greater than standard sorbents like activated carbon. The GO–BPEI composite can be easily regenerated as proven by performing adsorption cycles. Also, the thermodynamic parameters including standard Gibbs free energy (ΔGo), the enthalpy change (ΔHo) and entropy change (ΔSo) revealed the exothermic and spontaneous nature of the adsorption process.

This study reports a novel green chemistry approach to assemble copper-nanowires/reduced-graphene-oxide hybrid coatings onto inorganic and organic supports. Such films are robust and combine sheet resistances ( 70%) that are rivalling those of indium-tin oxide. These electrodes are suitable for flexible electronic applications as they show a sheet resistance change of

Two novel neutral complexes based on platinum metal ions, a tridentate ligand, and a pyridine bearing a β-lactam unit have been synthesized and their photophysical properties investigated. The complexes show interesting emission properties that, in the solid state, are dominated by the formation of aggregates due to the square-planar geometry of the PtII species. Importantly, the formation of closed-shell metal···metal interactions in such aggregates leads to new excited states that conveniently allow excitation in the visible region. The combination of the biologically active azetidinone agent and the intense and long-lived emission are of particular interest for developing efficient multifunctional biomedical systems.

Luminescent platinum complexes have attractive chemical and photophysical properties such as high stability, emission in the visible region, high emission quantum yields and long excited state lifetimes. However the absorption spectrum of the compounds in the UV region, preventing their excitation in the harmless visible/red region, as well as the strong quenching of the luminescent triplet state, caused by dioxygen in water and biological fluids, reduces their possible applications for imaging. Therefore a possible solution to these drawbacks is to take advantage of the high tendency of such square planar compounds to self-assemble in supramolecular structures. The assemblies can be considered new chemical species with enhanced and tunable properties. Furthermore the assembly and disassembly process can be explored as a tool to obtain dynamic labels that can be applied in biomedicine. The change in color, the turn on and off of luminescence but also of the reactivity, the protection from quenching and environmental degradation are some of the attractive properties connected to the aggregation of the complexes.

Molecular bio-imaging based on optical detection is facing important challenges in the attempt to develop new materials and small molecules able to have better emission quantum yield, stability toward photobleaching and long excited-state lifetime. A strategy to achieve these properties is to use triplet emitters based on metal complexes and to protect them from dioxygen quenching. We report on an interesting approach based on the use of self-assembled platinum compounds in order to obtain stable, highly emissive and long-lived species. Cell internalization and localization experiments show that the assemblies possess a different selectivity towards cellular compartments dictated by the terdentate ligand coordinated to the platinum. Also, the conditions used for the incubation determine cell internalization of the platinum complexes or their expulsion in the media.

International audience; The solvent-assisted self-assembly of a blue-emitting neutral platinum(II) complex into micrometer-long and highly crystalline fibers has been achieved. The aggregates show highly efficient (quantum yield up to 74%) polarized yellow-orange light emission, as a consequence of their high degree of supramolecular order imparted by weak non-covalent intermolecular (metal...metal and pi-pi) interactions.

The challenges of global climate change and the world's growing demand for energy have brought the need for new renewable energy sources to the top of the international community's agenda. We have known for many centuries that energy is released upon mixing seawater and freshwater, yet it was just a few decades ago that it became clear how this energy can be converted into electricity instead of heat. As a result, the blue energy rush has raised and set new strategies in different science and technology sectors, leading to the construction of a new generation of plants and other technological investments. Among many approaches, pressure-retarded osmosis has emerged as a promising method to collect the largest amount of produced blue energy. In this Perspective, we highlight the advances in the development of ultrathin membranes based on two-dimensional materials. We discuss the most relevant synthetic methods devised to generate atomically thin membranes for pressure-retarded osmosis and retarded electrodialysis applications, and we provide some critical views on the greatest challenges in this thrilling research area.

The design, synthesis and photophysical characterization of four new luminescent glycosylated luminophores based on dinuclear rhenium complexes, namely Glyco-Re, are described. The derivatives have the general formula [Re2(μ-Cl)2(CO)6(μ-pydz-R)] (R-pydz = functionalized 1,2-pyridazine), where a sugar residue (R) is covalently bound to the pyridazine ligand in the β position. Different synthetic pathways have been investigated including the so-called neo-glycorandomization procedure, affording stereoselectively glyco-conjugates containing glucose and maltose in a β anomeric configuration. A multivalent dinuclear rhenium glycodendron bearing three glucose units is also synthesized. All the Glyco-Re conjugates are comprehensively characterized and their photophysical properties and cellular internalization experiments on human cervical adenocarcinoma (HeLa) cells are reported. The results show that such Glyco-Re complexes display interesting bio-imaging properties, i.e. high cell permeability, organelle selectivity, low cytotoxicity and fast internalization. These findings make the presented Glyco-Re derivatives efficient phosphorescent probes suitable for cell imaging application.

Two novel neutral complexes based on platinum metal ions, a tridentate ligand, and a pyridine bearing a beta-lactam unit have been synthesized and their photophysical properties investigated. The complexes show interesting emission properties that, in the solid state, are dominated by the formation of aggregates due to the square-planar geometry of the Pt-II species. Importantly, the formation of closed-shell metal center dot center dot center dot metal interactions in such aggregates leads to new excited states that conveniently allow excitation in the visible region. The combination of the biologically active azetidinone agent and the intense and long-lived emission are of particular interest for developing efficient multifunctional biomedical systems

The self-assembly of chemical entities represents a very attractive way to create a large variety of ordered functional structures and complex matter. Although much effort has been devoted to the preparation of supramolecular nanostructures based on different chemical building blocks, an understanding of the mechanisms at play and the ability to monitor assembly processes and, in turn, control them are often elusive, which precludes a deep and comprehensive control of the final structures. Here the complex supramolecular landscape of a platinum(II) compound is characterized fully and controlled successfully through a combination of supramolecular and photochemical approaches. The supramolecular assemblies comprise two kinetic assemblies and their thermodynamic counterpart. The monitoring of the different emission properties of the aggregates, used as a fingerprint for each species, allows the real-time visualization of the evolving self-assemblies. The control of multiple supramolecular pathways will help the design of complex systems in and out of their thermodynamic equilibrium.

Supramolecular weak interactions can be used for preparing functional self-assembled architectures by powerful bottom-up approaches. In particular, when closed-shell metallophilic and π–π interacti...

A ratiometric chemosensor for potassium is reported, based on phosphorescent dinuclear cyclometalated Pt(II) complexes featuring a cis-crown ether as the cation-recognition unit. The metal complexes are blue luminescent in a non-aggregated state but become strongly orange emissive when in a close physical proximity, as is the case when the macrocycle is in the folded state. Upon binding of the cation, unfolding occurs, resulting in a pronounced change in the emission properties (e.g. emission wavelength), which can be used for ratiometric sensing applications. The reversibility of the binding was confirmed by competitive titration experiments with unsubstituted 18-crown-6; the system shows supramolecular switching behavior.

Supramolecular weak interactions can be used for preparing functional self-assembled architectures by powerful bottom-up approaches. In particular, when closed-shell metallophilic and π-π interactions between adjacent transition-metal complexes are established, profound changes in compounds' properties are obtained and novel features often achieved. In this Review, the most recent advances in the field of luminescent platinum(II) complexes aggregating through Pt-Pt interactions are highlighted and their potential application in different fields presented and discussed.

The self-assembly of multiple molecular components into complex supramolecular architectures is ubiquitous in nature and constitutes one of the most powerful strategies to fabricate multifunctional nanomaterials making use of the bottom-up approach. When spatial confinement in two dimensions on a solid substrate is employed, this approach can be exploited to generate periodically ordered structures from suitably designed molecular tectons. In this study we demonstrate that physisorbed directional periodic arrays of monometallic or heterobimetallic coordination polymers can be generated on a highly oriented pyrolitic graphite surface by combinations of a suitably designed directional organic tecton or metallatecton based on a porphyrin or nickel(II) metalloporphyrin backbone bearing both a pyridyl unit and a terpyridyl unit acting as coordinating sites for CoCl2. The periodic architectures were visualized at the solid/liquid interface with a submolecular resolution by scanning tunneling microscopy and corroborated by combined density functional and time-dependent density functional theory calculations. The capacity to nanopattern the surface for the first time with two distinct metallic centers exhibiting different electronic and optical properties is a key step toward the bottom-up construction of robust multicomponent and, thus, multifunctional molecular nanostructures and nanodevices.

A series of group 10 complexes featuring chelating tridentate bis-aryloxide N-heterocyclic carbenes were synthesized and characterized by using different techniques. Ni(II), Pd(II), and Pt(II) complexes were isolated in good yields by straightforward direct metalation of the corresponding benzimidazolium or imidazolium precursors in a one-pot procedure. All of the compounds were fully characterized, including single-crystal X-ray diffractometric determination for three of the derivatives. In the solid state, the complexes adopt a typical square-planar coordination geometry around the platinum atom, sizably distorted in order to comply with the geometrical constraints imposed by the bis-aryloxide N-heterocyclic carbene ligand. For platinum and palladium derivatives, a joint experimental and theoretical characterization was performed in order to study the optical properties of the newly prepared complexes by means of electronic absorption and steady-state and time-resolved photophysical techniques as well a...

International audience; 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.

International audience; 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.