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A straightforward way for the preparation of mechanochromic polymers consists of incorporating a suitable content of a mechanophore in the polymeric matrix either by physical dispersion or via covalent functionalization. Although covalent incorporation may require demanding chemical efforts, this approach can offer significant advantages over physical dispersion. In this work, a common thermoplastic elastomer, styrene-b-(ethylene-co-butylene)-b-styrene triblock copolymer grafted with maleic anhydride (SEBS-MAH), was covalently functionalized with 1-aminomethylpyrene (AMP). MAH functional groups are covalently linked to the ethylene-co-butylene blocks, thus allowing a precise and selective confinement of the chromogenic AMP units in the soft block. Flat, fully conjugated pyrene units undergo the reversible formation of pi-pi aggregates, readily distinguishable by their red-shifted emission. These aggregates were heavily affected by the application of mechanical stimuli. Despite the low degree of mechanophore functionalization (about 1 wt %), uniaxial deformation of the polymer was reliably monitored via fluorescence and a clear drop in the excimer to monomer emission ratio (I-E/I-M) was observed starting from 50% of strain. The marked mechanochromism was confirmed by emission lifetime measurements and also by near-field investigations. In addition, the mechanoresponse showed good reversibility after repeated stress-relaxation cycles. Control experiments performed on formulations comprising a physical dispersion of pyrene in unfunctionalized SEBS showed faint excimer emission and a negligible mechanochromic response up to 5 wt % of doping, in substantial agreement with the scanning near-field optical microscopy analysis. An evident drop of the I-E/I-M ratio occurred for 10 wt % of pyrene, albeit the excimer emission remained predominant even at the highest deformation, being a smaller fraction of pyrene moieties involved. Overall, the covalent approach appeared as an elegant procedure to confine the chromogenic unit in the soft phase of block copolymers and thus to provide an elastomeric film showing a detectable and reversible mechanochromic response with a modest (i.e., similar to 1 wt %) amount of pyrene molecules, i.e., 10 times smaller compared to the dispersed system.

The growing numbers related to plastic pollution are impressive, with ca. 70 % of produced plastic (>350 tonnes/year) being indiscriminately wasted in the environment. The most dangerous forms of plastic pollution for biota and human health are micro- and nano-plastics (MNPs), which are ubiquitous and more bioavailable. Their elimination is extremely difficult, but the first challenge is their detection since existing protocols are unsatisfactory for microplastics and mostly absent for nanoplastics. After a discussion of the state of the art for MNPs detection, we specifically revise the techniques based on photoluminescence that represent very promising solutions for this problem. In this context, Nile Red staining is the most used strategy and we show here its pros and limitations, but we also discuss other more recent approaches, such as the use of fluorogenic probes based on perylene-bisimide and on fluorogenic hyaluronan nanogels, with the added values of biocompatibility and water solubility.

Over the past two decades, the chirality-induced spin selectivity (CISS) effect was reported in several experiments disclosing a unique connection between chirality and electron spin. Recent theoretical works have highlighted time-resolved Electron Paramagnetic Resonance (trEPR) as a powerful tool to directly detect the spin polarisation resulting from CISS. Because of the absence of interfaces with conducting electrodes, such spectroscopic evidence could provide a clear understanding of how CISS works at the intramolecular level. Experimental results have demonstrated the potential of this approach for detecting a spin-polarised photoinduced electron transfer (ET) in hybrid systems comprising a CdSe quantum dot as an electron donor (D) connected by a chiral linker (χ) to a fullerene derivative as an electron acceptor (A). However, the study of the ET process in fully organic D-χ-A dyads holds tremendous potential for the unambiguous detection of CISS. Here, we report a first attempt performed using novel D-χ-A dyads, comprising pyrene (D) and fullerene (A) connected by chiral saturated peptide bridges (χ) of different length and electric dipole moment. The dyads are investigated by an array of techniques, including cyclic voltammetry, optical spectroscopies, and trEPR. Despite the promising energy alignment of the electronic levels and the evidence of luminescence quenching, trEPR does not detect a significant ET highlighting the challenges of spectroscopic detection of CISS. However, the analysis allows the formulation of guidelines for the design of chiral organic model systems suitable to directly probe CISS-polarised ET.

Environmental pollution from plastics is exponentially increasing due to human activities. While larger microplastics can be detected with various methods, retrieving micron-sized fragments and nanoplastics remains challenging. Yet, these smaller-sized plastics have been raising considerable toxicological concern. Here, we show that a poorly emissive hyaluronan functionalized with rhodamine B (HA–RB) adheres with high affinity to various microplastic surfaces, becoming brightly emissive. Micro- and nanoplastics (MNPs) can be successfully detected with size as small as the diffraction limit of confocal microscopy (ca. 250 nm). FLIM images show that the fluorescence lifetime of the dye moieties changes according to the plastics, making possible a discrimination of the nature of MNPs based on lifetime. HA–RB, compared to previous reports, eliminates false-positive results caused by formation of dye aggregates, resulting in a higher S/N ratio which allows the unequivocal detection of nano-sized fragments.

Two synthetic routes for the preparation of the water soluble 5,10,15‐tris(4‐sulfonatophenyl)corrole are reported. The first approach explores the chlorosulfonation reaction on the phosphorus complex of 5,10,15‐tris(4‐trimethylsilylphenyl)corrole. Following this route, the P complex of the target corrole has been obtained in low yields, while the major product was the tetrasubstituted complex, with the additional sulfonyl group regioselectively introduced at the 2‐position. To widen the scope of the reaction, the direct preparation of the 5,10,15‐tris(4‐sulfonatophenyl)corrole has been pointed out, affording both the target corrole and the intermediate chlorosulfonyl derivative in reasonable yields. The photophysical properties and the protonation equilibria of both corroles have been investigated, showing that 5,10,15‐tris(4‐sulfonatophenyl)corrole does not aggregate in acidic solutions, different from the analogous porphyrin.

Nanostructured systems constitute versatile carriers with multiple functions engineered in a nanometric space. Yet, such multimodality often requires adapting the chemistry of the nanostructure to the properties of the hosted functional molecules. Here, we show the preparation of core-shell Pluronic-organosilica "PluOS" nanoparticles with the use of a library of organosilane precursors. The precursors are obtained via a fast and quantitative click reaction, starting from cost-effective reagents such as diamines and an isocyanate silane derivative, and they condensate in building blocks characterized by a balance between hydrophobic and H-bond-rich domains. As nanoscopic probes for local polarity, oxygen permeability, and solvating properties, we use, respectively, solvatochromic, phosphorescent, and excimer-forming dyes covalently linked to the organosilica matrix during synthesis. The results obtained here clearly show that the use of these organosilane precursors allows for finely tuning polarity, oxygen permeability, and solvating properties of the resulting organosilica core, expanding the toolbox for precise engineering of the particle properties.

Microplastics (MP) are micrometric plastic particles present in drinking water, food and the environment that constitute an emerging pollutant and pose a menace to human health. Novel methods for the fast detection of these new contaminants are needed. Fluorescence-based detection exploits the use of specific probes to label the MP particles. This method can be environmentally friendly, low-cost, easily scalable but also very sensitive and specific. Here, we present the synthesis and application of a new probe based on perylene-diimide (PDI), which can be prepared in a few minutes by a one-pot reaction using a conventional microwave oven and can be used for the direct detection of MP in water without any further treatment of the sample. The green fluorescence is strongly quenched in water at neutral pH because of the formation dimers. The ability of the probe to label MP was tested for polyvinyl chloride (PVC), polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), poly methyl methacrylate (PMMA) and polytetrafluoroethylene (PTFE). The probe showed considerable selectivity to PVC MP, which presented an intense red emission after staining. Interestingly, the fluorescence of the MP after labeling could be detected, under excitation with a blue diode, with a conventional CMOS color camera. Good selectivity was achieved analyzing the red to green fluorescence intensity ratio. UV–Vis absorption, steady-state and time-resolved fluorescence spectroscopy, fluorescence anisotropy, fluorescence wide-field and confocal laser scanning microscopy allowed elucidating the mechanism of the staining in detail.

Semisolid redox flow batteries simultaneously address the need for high energy density and design flexibility. The electrical percolating network and electrochemical stability of the flowable electrodes are key features that are required to fully exploit the chemistry of the semisolid slurries. Superconcentrated electrolytes are getting much attention for their wide electrochemical stability window that can be exploited to design high-voltage batteries. Here, we report on the effect of the ion concentration of superconcentrated electrolytes on the electronic percolating network of carbonaceous slurries. Slurries based on different concentrations of lithium bis(trifluoromethane)sulfonamide in tetraethylene glycol dimethyl ether (0.5, 3, and 5 mol/kg) at different content of Pureblack carbon (from 2 up to 12 wt %) have been investigated. The study was carried out by coupling electrochemical impedance spectroscopy (EIS), optical fluorescence microscopy, and rheological measurements. A model that describes the complexity and heterogeneity of the semisolid fluids by multiple conductive branches is also proposed. For the first time, to the best of our knowledge, we demonstrate that besides their recognized high electrochemical stability, superconcentrated electrolytes enable more stable and electronically conductive slurry. Indeed, the high ionic strength of the superconcentrated solution shields interparticle interactions and enables better carbon dispersion and connections.

Nitroxides are an important class of radical trapping antioxidants whose promising biological activities are connected to their ability to scavenge peroxyl (ROO•) radicals. We have measured the rate constants of the reaction with ROO• (kinh) for a series of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) derivatives as 5.1 × 106, 1.1 × 106, 5.4 × 105, 3.7 × 105, 1.1 × 105, 1.9 × 105, and 5.6 × 104 M–1 s–1 for −H, −OH, −NH2, −COOH, −NHCOCH3, −CONH(CH2)3CH3, and =O substituents in the 4 position, with a good Marcus relationship between log (kinh) and E° for the R2NO•/R2NO+ couple. Newly synthesized Pluronic-silica nanoparticles (PluS) having nitroxide moieties covalently bound to the silica surface (PluS–NO) through a TEMPO–CONH–R link and coumarin dyes embedded in the silica core, has kinh = 1.5 × 105 M–1 s–1. Each PluS-bound nitroxide displays an inhibition duration nearly double that of a structurally related "free" nitroxide. As each PluS–NO particle bears an average of 30 nitroxide units, this yields an overall ≈60-fold larger inhibition of the PluS–NO nanoantioxidant compared to the molecular analogue. The implications of these results for the development of novel nanoantioxidants based on nitroxide derivatives are discussed, such as the choice of the best linkage group and the importance of the regeneration cycle in determining the duration of inhibition.

Luminescence quenching is a process exploited in transversal applications in science and technology and it has been studied for a long time. The luminescence quenching mechanisms are typically distinguished in dynamic (collisional) and static, which can require different quantitative treatments. This is particularly important – and finds broad and interdisciplinary application – when the static quenching is caused by the formation of an adduct between the luminophore – at the ground state – and the quencher. Due to its nature, this case should be treated starting from the well-known law of mass action although, in specific conditions, general equations can be conveniently reduced to simpler ones. A proper application of simplified equations, though, can be tricky, with frequent oversimplifications taking to severe errors in the interpretation of the photophysical data. This tutorial review aims to (i) identify the precise working conditions for the application of the simplified equations of static quenching and to (ii) provide general equations for broadest versatility and applicability. The latter equations can be used even beyond the sole case of pure quenching, i.e., in the cases of partial quenching and even luminescence turn-on. Finally, we illustrate different applications of the equations via a critical discussion of examples in the field of sensing, supramolecular chemistry and nanotechnology.

Protein aggregation is a phenomenon widespread in all organisms, that responds to a variety of external stimuli and is involved in complex functions such as storage and recycling of protein residues in crowded environments. In some cases, aggregation of proteins is related to serious human diseases. Understanding, monitoring and, eventually, intervening in the process of aggregation – in particular at its early stage – is a topic of high relevance and urgency. Recently, nanostructured materials have allowed for an unmet versatility and modularity in the field of sensing and inhibition of aggregation. Fluorescent oligomers and polymers, via controlled tuning of chemical functionalities, are yielding detailed comprehension of the interactions between probe candidates and protein aggregates; AIEgens are rapidly addressing many open challenges on sensitivity and signal enhancement; nanomaterials are increasingly serving as theranostic platforms, with multiple functionalities stemming from the assembly of components with complementary abilities. Here we review the most recent achievements in protein aggregation sensing based on macromolecular or nanostructured probes, highlighting the general experimental and computational findings that may serve as guidelines for the next generation of theranostic probes.

The detection of the Cerenkov radiation (CR) is an emerging preclinical imaging technique which allows monitoring the in vivo distribution of radionuclides. Among its possible advantages, the most interesting is the simplicity and cost of the required instrumentation compared, e.g., to that required for PET scans. On the other hand, one of its main drawbacks is related to the fact that CR, presenting the most intense component in the UV-vis region, has a very low penetration in biological tissues. To address this issue, we present here multifluorophoric silica nanoparticles properly designed to efficiently absorb the CR radiation and to have a quite high fluorescence quantum yield (0.12) at 826 nm. Thanks to a highly efficient series of energy transfer processes, each nanoparticle can convert part of the CR into NIR light, increasing its detection even under 1.0-cm thickness of muscle.

Hybrid nanomaterials are a subject of extensive research in nanomedicine, and their clinical application is reasonably envisaged in the near future. However, the fate of nanomaterials in biological environments poses serious limitations to their application; therefore, schemes to monitor them and gain control on their toxicity could be of great help for the development of the field. Here, we propose a probe for PEGylated nanosurfaces based on hyaluronic acid (HA) functionalized with rhodamine B (RB). We show that the high-affinity interaction of this fluorogenic hyaluronan (HA-RB) with nanoparticles exposing PEGylated surfaces results in their sensing, labeling for super-resolution imaging, and synergistic cellular internalization. HA-RB forms nanogels that interact with high affinity-down to the picomolar range-with silica nanoparticles, selectively when their surface is covered by a soft and amphiphilic layer. This surface-driven interaction triggers the enhancement of the luminescence intensity of the dyes, otherwise self-quenched in HA-RB nanogels. The sensitive labeling of specific nanosurfaces also allowed us to obtain their super-resolution imaging via binding-activated localization microscopy (BALM). Finally, we show how this high-affinity interaction activates a synergistic cellular uptake of silica nanoparticles and HA-RB nanogels, followed by a differential fate of the two partner nanomaterials inside cells.

Chlorin e6 (Ce6) and its derivatives are among the most important photosensitizers in photodynamic therapy. Due to their intense fluorescence, chlorins may also be used for diagnostics. However, low solubility in water and high tendency to aggregation restrict their medical use. Here we demonstrate that apo-myoglobin, by reinserting Ce6 in its heme binding pocket, can be used to monomolecularly disperse it. The reconstructed myoglobin-Ce6 adduct presents noticeable changes in the photophysical properties of the chromophore. A red-shift, in particular in the transparency window, can be observed in the absorption and in the emission spectra of the adduct compared to the spectra of the free chlorin in PBS. The adduct presents a higher quantum yield and an increased excited-state lifetime with respect to the free Ce6. The binding of Ce6 to apo-myoglobin determines a decrease of the 1O2 generation but a three-fold increase of peroxides production, determining globally an increase in the performance of Ce6 as a photosensitizer and imaging agent.

Electrochemiluminescence (ECL) is a leading technique in bioanalysis.[1] It is a luminescent phenomenon where the excited species are produced with an electrochemical stimulus rather than with a light excitation source. For this reason, ECL displays improved signal-to-noise ratio compared to photoluminescence, with minimized effects due to light scattering and luminescence background.[2] Chasing ever-increasing sensitivities, ECL can ideally be coupled to nanotechnology to develop new strategies for clinical applications and analyte determination also in real and complex matrices.[3] In particular, dye-doped silica nanoparticles (DDSNs) present many advantages: they can be easily synthesized, are hydrophilic and are prone to bioconjugation thanks to silica chemistry. With this approach we were able to achieve extremely bright systems and DDSNs allow the 8.5 fold increase of ECL intensity.[4] In DDSNs, light emission is influenced by the combination of several factors that make DDSNs complex multichromophoric structures. However, when ECL comes into play, the scenario is even more complicated due to the coreactant−NP interactions effect. Such complex scenario was approached at the theoretical level by developing suitable mechanistic models for ECL generation[5] while, at the same time, the influence of doping level on ECL efficiency was evaluated. Our results showed that the ECL intensity of a nanosized system cannot be merely incremented acting on doping, since other parameters come into play. These studies support the application in ECL microscopy providing valuable indications for the design of more efficient ECL nano- and micro-sized labels towards more sensitive ECL-based immunoassay for bioanalysis applications. [6] References [1] W. Miao, “Electrogenerated Chemiluminescence and Its Biorelated Applications”, Chem. Rev., 2008, vol. 108, pp. 2506–2553. [2] Z. Liu, W. Qi, G. Xu, “Recent advances in electrochemiluminescence”, Chem. Soc. Rev., 2015, vol. 44, pp. 3117–3142. [3] C. Ma, Y. Cao, X. Gou, J. J. Zhu, “Recent progress in electrochemiluminescence sensing and imaging”, Anal. Chem., 2015, vol. 92, pp. 431-454. [4] G. Valenti, E. Rampazzo, S. Bonacchi, L. Petrizza, M. Marcaccio, M. Montalti, L. Prodi, F. Paolucci, “Variable Doping Induces Mechanism Swapping in Electrogenerated Chemiluminescence of Ru(bpy) 3 2+ Core–Shell Silica Nanoparticles”, J. Am. Chem. Soc., 2016, vol. 138, pp. 15935–15942. [5] E. Daviddi, A. Oleinick, I. Svir, G. Valenti, F. Paolucci, C. Amatore, “Theory and Simulation for Optimising Electrogenerated Chemiluminescence from Tris(2,2′-bipyridine)-ruthenium(II)-Doped Silica Nanoparticles and Tripropylamine”, ChemElectroChem, 2017, vol. 4, pp. 1719–1730. [6] A. Zanut, F. Palomba, M. Rossi Scota, S. Rebeccani, M. Marcaccio, D. Genovese, E. Rampazzo, G. Valenti, F. Paolucci, L. Prodi, "Dye‐Doped Silica Nanoparticles for Enhanced ECL‐Based Immunoassay Analytical Performance", Angew. Chemie Int. Ed., 2020, vol. 132, pp. 22042-22047 Figure 1

Understanding polarity gradients inside nanomaterials is essential to capture their potential as nanoreactors, catalysts or in drug delivery applications. We propose here a method to obtain detailed, quantitative information on heterogeneous polarity in multicompartment nanostructures. The method is based on a 2-steps procedure, (i) deconvolution of complex emission spectra of two solvatochromic probes followed by (ii) spectrally resolved analysis of FRET between the same solvatochromic dyes. While the first step yields a list of polarities probed in the nanomaterial suspension, the second step correlates the polarities in space. Colocalization of polarities falling within few nanometer radius is obtained via FRET, a process called here nanopolarity mapping. Here, Prodan and Nile Red are tested to map the polarity of a water-dispersable, multicompartment nanostructure, named PluS nanoparticle (NPs). PluS NPs are uniform core-shell nanoparticles with silica cores (diameter ~10 nm) and Pluronic F127 shell (thickness ~7 nm). The probes report on a wide range of nanopolarities among which the dyes efficiently exchange energy via FRET, demonstrating the coexistence of a rich variety of environments within nanometer distance. Their use as a FRET couple highlights the proximity of strongly hydrophobic sites and hydrated layers, and quantitatively accounts for the emission component related to external water, which remains unaffected by FRET processes. This method is general and applicable to map nanopolarity in a large variety of nanomaterials.

Electrolytes are key components of Li/O2 batteries. The ionic liquid-like structure and good electrochemical and thermal stability of solvent-in-salt electrolytes make them of great interest for lithium batteries. Solutions of lithium bis(trifluoromethanesulfonyl)imide in tetraethylene glycol dimethyl-ether with molar ratios ranging from 1:9 to 1:0.9 are here investigated. A voltammetric study of oxygen redox reaction in presence of different concentrations of salt, from salt-in-solvent to solvent-in-salt solutions, is reported here for the first time along with a novel luminescence method for the evaluation of O2 solubility. The results indicate that superconcentrated solutions favor the solution formation mechanism of Li2O2 during discharge which in turn is beneficial for battery cycling stability. Despite the higher viscosity of solvent-in-salt solutions than conventional electrolytes, O2 solubility is improved at the highest salt concentrations. These findings contribute to understand electrochemical processes in solvent-in-salt solutions for Li/O2 and next generation metal-based batteries.

Protein aggregation is a complex physiological process, primarily determined by stress-related factors revealing the hidden aggregation propensity of proteins that otherwise are fully soluble. Here we report a mechanism by which glycolytic glyceraldehyde-3-phosphate dehydrogenase of Arabidopsis thaliana (AtGAPC1) is primed to form insoluble aggregates by the glutathionylation of its catalytic cysteine (Cys149). Following a lag phase, glutathionylated AtGAPC1 initiates a self-aggregation process resulting in the formation of branched chains of globular particles made of partially misfolded and totally inactive proteins. GSH molecules within AtGAPC1 active sites are suggested to provide the initial destabilizing signal. The following removal of glutathione by the formation of an alternative disulfide bond between Cys149 and Cys153 reinforces the aggregation process. Besides acting as a protective mechanism against overoxidation, S-glutathionylation of AtGAPC1 triggers an unexpected aggregation pathway with completely different and still unexplored physiological implications.

Protein aggregation is a complex physiological process, primarily determined by stress-related factors revealing the hidden aggregation propensity of proteins that otherwise are fully soluble. Here we report a mechanism by which glycolytic glyceraldehyde-3-phosphate dehydrogenase of Arabidopsis thaliana (AtGAPC1) is primed to form insoluble aggregates by the glutathionylation of its catalytic cysteine (Cys149). Following a lag phase, glutathionylated AtGAPC1 initiates a self-aggregation process resulting in the formation of branched chains of globular particles made of partially misfolded and totally inactive proteins. GSH molecules within AtGAPC1 active sites are suggested to provide the initial destabilizing signal. The following removal of glutathione by the formation of an intramolecular disulfide bond between Cys149 and Cys153 reinforces the aggregation process. Physiological reductases, thioredoxins and glutaredoxins, could not dissolve AtGAPC1 aggregates but could efficiently contrast their growth. Besides acting as a protective mechanism against overoxidation, S-glutathionylation of AtGAPC1 triggers an unexpected aggregation pathway with completely different and still unexplored physiological implications.

Silica nanoparticles (NPs) are versatile nanomaterials, which are safe with respect to biomedical applications, and therefore are highly investigated. The advantages of NPs include their ease of preparation, inexpensive starting materials and the possibility of functionalization or loading with various doping agents. However, the solubility of the doping agent(s) imposes constraints on the choice of the reaction system and hence limits the range of molecules that can be included in the interior of NPs. To overcome this problem, herein, we improved the current state of the art synthetic strategy based on Pluronic F127 by enabling the synthesis in the presence of large amounts of organic solvents. The new method enables the preparation of nanoparticles doped with large amounts of water-insoluble doping agents. To illustrate the applicability of the technology, we successfully incorporated a range of phosphorescent metalloporphyrins into the interior of NPs. The resulting phosphorescent nanoparticles may exhibit potential for biological oxygen sensing.

Fast and efficient energy transfer among dyes confined in nanocontainers provides the basis of outstanding functionalities in new-generation luminescent probes. This feature article provides an overview of recent research achievements on luminescent Pluronic-Silica NanoParticles (PluS NPs), a class of extremely monodisperse core-shell nanoparticles whose design can be easily tuned to match specific needs for diverse applications based on luminescence, and that have already been successfully tested in in vivo imaging. An outline of their outstanding properties, such as tuneability, bright and photoswitchable fluorescence and electrochemiluminescence, will be supported by a critical discussion of our recent works in this field. Furthermore, novel data and simulations will be presented to (i) thoroughly examine common issues arising from the inclusion of multiple dyes in a small silica core, and (ii) show the emergence of a cooperative behaviour among embedded dyes. Such cooperative behaviour provides a handle for fine control of brightness, emission colour and self-quenching phenomena in PluS NPs, leading to significantly enhanced signal to noise ratios.

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.

Lasing from cells has recently been subject of thorough investigation because of the potential for sensitive and fast biosensing. Yet, lasing from individual cells has been studied in high-quality resonators, resulting in limited dependence of the lasing properties on the cellular microenvironment. Here, lasing is triggered by cells floating in a low quality factor resonator composed of a disposable poly(methyl methacrylate) (PMMA) cell counting-slide, hence in absence of conventional high-reflectivity optical cavities. The exceptional spectral narrowing and the steep slope increase in the input–output energy diagram prove occurrence of laser action in presence of cells. The observed biolasing is an intrinsically dynamic signal, with large fluctuations in intensity and spectrum determined by the optical properties of the individual cell passing through the pump beam. Numerical simulations of the scattering efficiency rule out the possibility of optical feedback from either WGM (whispering gallery mode) or multiple scattering within the cell, and point to the enhanced directional scattering field as the crucial contribution of cells to the laser action. Finally, principal component analysis of lasing spectra measured from freely diffusing cells yields spectral fingerprints of cell populations, which allows discriminating cancer from healthy Rattus glial cells with high degree of confidence.

A nanosensor with dual-mode fluorescence response to pH and an encoded identification signal, was developed by exploiting excitation energy transfer and tailored control of molecular organization in core–shell nanoparticles. Multiple signals were acquired in a simple single-excitation dual-emission channels set-up.

Silicon complexes of corrole were obtained for the first time by reaction of the free-base corrole with hexachlorodisilane. The peripheral substituents of corrole strongly influence the nature of the reaction products: β-octaalkyl corrole was mainly isolated as the μ-oxo dimer, while a hydroxo complex was obtained in the case of 5,10,15-tris-(pentafluorophenyl)corrole. In the case of meso-tritolyl corrole, a mixture of monomer/μ-oxo dimer was obtained. The silicon corrole complexes are more stable toward hydrolysis than the corresponding porphyrin derivatives and are endowed with brilliant luminescence properties. The high affinity of silicon for fluoride ion allowed investigation of the ability of an Si corrole to serve as a sensor for F− detection. The strong color variation due to the interaction with the halide ion makes the Si corrole an interesting material for the naked-eye detection of inorganic fluoride.

Copper and gallium β-acrolein corroles have been obtained by reaction of corrole complexes with 3-(dimethylamino)-acrolein/phosphoryl chloride (3-DMA/POCl3) under Vilsmeier conditions. In the case of the Ga complex, up to four acroleyl substituents have been introduced at the β-peripheral positions of the corrole macrocycle. The introduction of the acroleyl moiety on the corrole scaffold strongly influences the photophysical behaviour of the Ga corroles.

The coupling of nanomaterials, and nanoparticles in particular, with one of the most powerful transduction techniques, electrochemiluminescence (ECL), i.e., chemiluminescence triggered by electrochemical reactions at electrodes, has recently provided sensing tools with unprecedented sensitivity limits. This review aims to give an overview of the state of the art in the field over the last 5 years, i.e., a time span covering over 80% of the scientific production in this context. The results herein discussed would demonstrate that the use of nanoparticles in the ECL technique represents one of the most interesting research lines for the development of ultrasensitive analytical tools, offering an insight to recognize and select the best nanomaterials for ECL signal amplification, with particular emphasis in biosensing. (C) 2018 Elsevier B.V. All rights reserved.

Mechanochromic polymeric systems are intensively investigated for real-time stress detection applications. However, an effective stress-sensing material must respond to low deformation with a detectable color change that should be quickly reversible upon force unloading. In this work, mechanochromic nanofibers made by electrospinning are used to produce mechanochromic nanofiber/poly(dimethylsiloxane) (PDMS) composites with isotropic and anisoptropic response. Due to chain alignment of spiropyran copolymer chains within the nanofibers, only very small strains are required to yield a mechanochromic response. Composites with aligned and isotropic nanofibers show anisotropic and isotropic mechanochromic behavior, respectively. Due to the special substitution pattern of spiropyran in the copolymer, the mechanochromic response of these nanofiber/PDMS composites shows fast reversibility upon force unloading. The outstanding benefit of using highly sensitive mechanochromic nanofibers as filler in composite materials allows the detection of directional stress and strain, and it is a step forward in the development of smart, mechanically responsive materials.

With the aim to improve the features of surfactant solutions in terms of sustainability and renewability we propose the use of hydrogenated natural and sustainable plant-derived cardanol as an additive to com- mercial surfactants. In the present study we demonstrated that its addition, in amounts as high as 10%, to commercial surfactants of different charge does not significantly affect surfactant properties. Conversely, the presence of hydrogenated cardanol can strongly affect spectrophotometric determination of CMC if preferential interactions with the dyes used take place. This latter evidence may be profitably exploited in surfactant manufacturing by considering that the concurrent presence of a rigid organic molecule such as Orange OT and 10% hydrogenated cardanol decreases the CMC of CTAB up to 65 times.

Dye-doped nanoparticles (NPs) are intriguing fluorescent systems in which collective properties can arise, which are ascribable to the ensemble of dyes rather than to individual ones. Collective properties can be tailored to increase brightness and introduce photophysical versatility. In this context, self-quenching has long been regarded as the phenomenon to avoid. Here we report on the possibility to profit from a property stemming from self-quenching: nanoparticles with a high number of dyes per NP (including self-quenched dyes) display much slower photobleaching compared to nanoparticles with a lower doping degree. In this way, their emission intensity can be kept almost constant for ten times longer. This extended duration of luminescence is due to preferential photobleaching of self-quenched fluorophores. These observations can shine new light on the use of highly dye-doped nanoparticles as long-lasting, super-photostable probes under strong excitation conditions.

Bottom-up self-assembly of simple molecular compounds is a prime pathway to complex materials with interesting structures and functions. Coupled reaction systems are known to spontaneously produce highly ordered patterns, so far observed in soft matter. Here we show that similar phenomena can occur during silica-carbonate crystallization, the emerging order being preserved. The resulting materials, called silica biomorphs, exhibit non-crystallographic curved morphologies and hierarchical textures, much reminiscent of structural principles found in natural biominerals. We have used a fluorescent chemosensor to probe local conditions during the growth of such self-organized nanostructures. We demonstrate that the pH oscillates in the local microenvironment near the growth front due to chemical coupling, which becomes manifest in the final mineralized architectures as intrinsic banding patterns with the same periodicity. A better understanding of dynamic autocatalytic crystallization processes in such simple model systems is key to the rational development of advanced materials and to unravel the mechanisms of biomineralization., This work was funded by the European Research Council (European Union’s Seventh Framework Programme (FP7/2007-2013, grant no. 340863) and the Spanish MINECO grant CGL2010-16882 (co-funded by FEDER)

The N,N'-dimethyl-3,3'-biquinoxalinium "methylbiquinoxen" dicationic platform is revealed to have even more fascinating possibilities than we originally thought in terms of its chemical versatility. In addition to its rich redox chemistry and coordination abilities, we have now unveiled an unexpected Lewis acid/base chemistry linked with a tuneable switching of its luminescence properties. This, amongst other things, allows for the facile fluorescent covalent labelling of hydroxyl-terminated materials. This platform provides intriguing chemical prospects realised in molecular systems such as porphyrins as well as an easy alternative functionalisation methodology to that provided by click-chemistry.

The synthesis, spectroscopic, and optical properties of the water-soluble phosphorus complex of a 2-sulfonato-10-(4-sulfonatophenyl)-5,15-dimesitylcorrole have been investigated. The compound was prepared by adopting a novel strategy for the corrole sulfonation, leading to the regioselective isomer in an almost quantitative yield. The phosphorus coordination has a key role in determining the corrole substitution pattern, limiting the formation of poly-substituted species, which affected the reaction of the corrole free base. The resulting complex shows excellent optical properties in terms of emission quantum yield, also in polar protic solvents, including water. 31P NMR spectroscopy in CD3OD indicates that the P sulfonate complex has been isolated in a hexacoordinated geometry with two different ligands (L1=-OH, L2=-OCH3), and it is prone to axial ligand exchange with methanol, with no evidence of intermediate pentacoordinated species. The morphological characterization of thin layers of the P corrole deposited onto an Au(111) surface showed that the addition of an intermediate layer of reduced graphene oxide allows for a better control of corrole aggregation, inducing also transformation of the Au(111) reconstructed surface. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

The photophysical properties of two 7-aminocoumarin molecules with flexible and rigid alkyl moieties at the 7-nitrogen atom have been investigated in ethanol and in Pluronic-silica nanoparticles (PluS NPs) by means of time-resolved emission spectroscopy (TRES) and time-dependent density functional theory (TDDFT). Although the two coumarin derivatives have very different photophysical properties in solution, they show quite similar photophysical behaviour when embedded into the NPs, where an increase in the fluorescence quantum yield of about 10 times was observed for the more flexible molecule. TDDFT calculations employing long-range corrected functionals and with proper account of environmental effects reveal that the formation of an accessible twisted-intramolecular charge transfer state (TICT) is possible for 7-aminocoumarin molecules with flexible alkyl groups in fluid solution, where a conical intersection between the S1 and S0 states is observed at a dihedral angle of about 80°. The excited state dynamics of the population density of this reaction coordinate in ethanol and in silica NPs investigated through the resolution of a generalized Smoulochowsky equation shows that this deactivation mechanism is drastically hampered in a silica matrix, in good agreement with experimental evidence. Steady state and time resolved measurements also suggest that at high concentration for both the dyes intermolecular interactions into the silica matrix lead to fluorescence quenching. TDDFT/PCM calculations clearly indicate that the strong quenching and red shift observed is imputable to the formation of excimers with CT character after absorption of the monomeric species.

We report here the design of two sets of multifluorophoric silica nanoparticles, observing unprecedented efficiencies in the energy-transfer processes among the doping dyes. These nanomaterials show a very high overall sensitization, allowing under a single wavelength excitation to obtain many different colors (one per nanoparticle) in emission with negligible crosstalk. Moreover, each particle can present very large and tunable pseudo-Stokes shifts (up to 435 nm), a very high brightness even exciting the bluest donor, and a negligible residual emission intensity from all donor dyes. All these features, combined with colloidal stability and synthetic method reliability, make these multicomponent nanoparticles very promising for multiplex analysis and for all the diagnostic techniques requiring high sensitivity associated with a large Stokes shift.

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...

The molecular structure of the units that get incorporated into the nuclei of the crystalline phase and sustain their growth is a fundamental issue in the pathway from a supersaturated solution to the formation of crystals. Using a fluorescent dye we have recorded the variation of the pH value in time along a gel where CaCl2 and NaHCO3 counter-diffuse to crystallize CaCO3. The same pH–space–time distribution maps were also computationally obtained using a chemical speciation code (phreeqc). Using data arising from this model we investigated the space-time evolution of the activity of the single species (ions and ion pairs) involved in the crystallization process. Our combined results suggest that, whatever the pathway from solution to crystals, the neutral pair CaCO3° is a key species in the CaCO3 precipitation system., European Research Council (European Union’s Seventh Framework Programme (FP7/2007-2013) grant agreement no 340863, and Spanish MINECO grants MAT2014-60533-R and CGL2010-16882 cofounded with FEDER

Indium tin oxide (ITO) and silicon with a thermally grown SiO2 layer (Si/SiO2) substrates have been functionalized by ferrocene bound through Sn(O)x (x=2 or 3) linkers preliminarly grafted on the surface by reaction of the terminal hydroxyl groups with tetra(tert-butoxy)tin. The two steps modification of the surface was carried out by chemical vapour deposition metathesis reaction producing a self-assembled monolayer of ferrocene. The ITO and Si/SiO2 thus functionalized have been characterized by voltammetric, amperometric, electrochemical impedance spectroscopy and scanning probe microscopy techniques which assessed the formation of a stable and rather compact covalently bound ferrocenyl monolayer with improved electron transfer properties.

Mineralized tissues grow through biologically controlled processes in which specific macromolecules are involved. Some of these molecules, which are present in very low concentrations and are difficult to localize and characterize, become entrapped inside the mineralized tissue. Herein, a protein fragment, GP, which was obtained by the alkaline digestion of the green sheet of the abalone shell, is used as a probe to study the changes in molecular structure that occur during the precipitation of calcium carbonate. This important goal was achieved by exploiting a fluorescent tag in GP. The experimental results that were obtained by using spectroscopic-, chromatographic-, and microscopic techniques indicate that GP controls the precipitation kinetics and morphology of calcium carbonate crystals, and that it only undergoes structural reorganization when entrapped inside calcium carbonate crystals. To the best of our knowledge, this report represents one of the first studies on the conformational changes of a protein fragment that is involved in biomineralization processes on moving from the solution phase into the mineral phase.

Siliciumdioxidnanopartikel verfugen uber besondere Eigenschaften, z. B. eine geringe Toxizitat, und stellen eine vielseitige Plattform fur die Nanotechnologie dar. Ein geeignetes Design oder eine geeignete Derivatisierung fuhren zu selbst unter physiologischen Bedingungen stabilen Kolloiden und ermoglichen verschiedenste Funktionen. Insbesondere bei der Wahl passender Farbstoffe und Synthesestrategien konnen sehr hell leuchtende Nanosysteme resultieren. So bieten Siliciumdioxidnanopartikel ein einzigartiges Potenzial, und weitere Verbesserungen konnten neue Anwendungen in Bereichen wie medizinischer Diagnose und Therapie, Umwelt- und Lebensmittelanalytik sowie Sicherheit bringen. Hier stellen wir Mehrkomponenten-Nanosysteme auf Siliciumdioxidbasis vor, die zu gerichtetem Energie- und Elektronentransfer fahig sind und sich fur Funktionen wie Lichtsammeln und Signalverstarkung eignen.