Showing papers by "Mirko Prato published in 2018"
TL;DR: It is shown here that benzoyl halides can be efficiently used as halide sources to be injected in a solution of metal cations for the synthesis of APbX3 NCs, and it is possible to independently tune the amount of both cations and halide precursors in the synthesis.
Abstract: We propose here a new colloidal approach for the synthesis of both all-inorganic and hybrid organic–inorganic lead halide perovskite nanocrystals (NCs) The main limitation of the protocols that are currently in use, such as the hot injection and the ligand-assisted reprecipitation routes, is that they employ PbX2 (X = Cl, Br, or I) salts as both lead and halide precursors This imposes restrictions on being able to precisely tune the amount of reaction species and, consequently, on being able to regulate the composition of the final NCs In order to overcome this issue, we show here that benzoyl halides can be efficiently used as halide sources to be injected in a solution of metal cations (mainly in the form of metal carboxylates) for the synthesis of APbX3 NCs (in which A = Cs+, CH3NH3+, or CH(NH2)2+) In this way, it is possible to independently tune the amount of both cations and halide precursors in the synthesis The APbX3 NCs that were prepared with our protocol show excellent optical properties,
431 citations
TL;DR: This work shows the first colloidal synthesis of double perovskite Cs2AgInCl6 nanocrystals (NCs) with a control over their size distribution with a broad spectrum white photoluminescence (PL) with quantum yield of ∼1.6 ± 1% and a bright orange emission characterized the Mn-doped Cs 2Ag inCl6 NCs with a PL quantum yield as high as ∼16 ± 4%.
Abstract: We show here the first colloidal synthesis of double perovskite Cs2AgInCl6 nanocrystals (NCs) with a control over their size distribution. In our approach, metal carboxylate precursors and ligands (oleylamine and oleic acid) are dissolved in diphenyl ether and reacted at 105 °C with benzoyl chloride. The resulting Cs2AgInCl6 NCs exhibit the expected double perovskite crystal structure, are stable under air, and show a broad spectrum white photoluminescence (PL) with quantum yield of ∼1.6 ± 1%. The optical properties of these NCs were improved by synthesizing Mn-doped Cs2AgInCl6 NCs through the simple addition of Mn-acetate to the reaction mixture. The NC products were characterized by the same double perovskite crystal structure, and Mn doping levels up to 1.5%, as confirmed by elemental analyses. The effective incorporation of Mn ions inside Cs2AgInCl6 NCs was also proved by means of electron spin resonance spectroscopy. A bright orange emission characterized our Mn-doped Cs2AgInCl6 NCs with a PL quantum...
332 citations
TL;DR: The "graphene interface engineering" (GIE) strategy enables MAPbI3-based PSCs to achieve a PCE up to 20.12% (average PCE of 18.8%) and the possibility to combine quantum and chemical effects into GIE, coupled with the recent success of graphene and GRMs as interfacial layer, represents a promising approach for the development of next-generation P SCs.
Abstract: Interface engineering of organic–inorganic halide perovskite solar cells (PSCs) plays a pivotal role in achieving high power conversion efficiency (PCE). In fact, the perovskite photoactive layer needs to work synergistically with the other functional components of the cell, such as charge transporting/active buffer layers and electrodes. In this context, graphene and related two-dimensional materials (GRMs) are promising candidates to tune “on demand” the interface properties of PSCs. In this work, we fully exploit the potential of GRMs by controlling the optoelectronic properties of molybdenum disulfide (MoS2) and reduced graphene oxide (RGO) hybrids both as hole transport layer (HTL) and active buffer layer (ABL) in mesoscopic methylammonium lead iodide (CH3NH3PbI3) perovskite (MAPbI3)-based PSCs. We show that zero-dimensional MoS2 quantum dots (MoS2 QDs), derived by liquid phase exfoliated MoS2 flakes, provide both hole-extraction and electron-blocking properties. In fact, on one hand, intrinsic n-typ...
182 citations
TL;DR: In this paper, the authors designed and engineered heterostructures composed of single/few-layer MoSe2 flakes and carbon nanomaterials (graphene or single-wall carbon nanotubes (SWNTs)) produced by solution processing.
Abstract: Two-dimensional transition metal-dichalcogenides are emerging as efficient and cost-effective electrocatalysts for hydrogen evolution reaction (HER). However, only the edge sites of their trigonal prismatic phase show HER-electrocatalytic properties, while the basal plane, which is absent of defective/unsaturated sites, is inactive. Here, we tackle the key challenge that is increasing the number of electrocatalytic sites by designing and engineering heterostructures composed of single-/few-layer MoSe2 flakes and carbon nanomaterials (graphene or single-wall carbon nanotubes (SWNTs)) produced by solution processing. The electrochemical coupling between the materials that comprise the heterostructure effectively enhances the HER-electrocatalytic activity of the native MoSe2 flakes. The optimization of the mass loading of MoSe2 flakes and their electrode assembly via monolithic heterostructure stacking provided a cathodic current density of 10mAcm-2 at overpotential of 100mV, a Tafel slope of 63mVdec-1 and an exchange current density (j0) of 0.203 Acm-2. In addition, electrode thermal annealing in a hydrogen environment and chemical bathing in n-butyllithium are exploited to texturize the basal planes of the MoSe2 flakes (through Se-vacancies creation) and to achieve in situ semiconducting-to-metallic phase conversion, respectively, thus they activate new HER-electrocatalytic sites. The as-engineered electrodes show a 4.8-fold enhancement of j0 and a decrease in the Tafel slope to 54mVdec-1.
131 citations
TL;DR: In this article, a high-pressure wet-jet-milling (WJM) process is proposed for the exfoliation of layered 2D crystals, i.e., graphite, hexagonal-boron nitride and transition metal dichalcogenides.
Abstract: Efficient and scalable production of two-dimensional (2D) materials is required to overcome technological hurdles towards the creation of a 2D-material-based industry. Here, we present a novel approach developed for the exfoliation of layered crystals, i.e., graphite, hexagonal-boron nitride and transition metal dichalcogenides. The process is based on high-pressure wet-jet-milling (WJM), resulting in a 2 L h−1 production of 10 g L−1 of single- and few-layer 2D crystal flakes in dispersion making the scaling-up more affordable. The WJM process enables the production of defect-free and high quality 2D-crystal dispersions on a large scale, opening the way for their full exploitation in different commercial applications, e.g., as anode active material in lithium ion batteries, as reinforcement in polymer–graphene composites, and as conductive inks, as we demonstrate in this report.
129 citations
TL;DR: Chlorine ions can add a new degree of freedom to the growth of 2D colloidal nanocrystal emitters, yielding new insights into both the NPL synthesis as well as their optoelectronic properties.
Abstract: Current colloidal synthesis methods for CdSe nanoplatelets (NPLs) routinely yield samples that emit, in discrete steps, from 460 to 550 nm. A significant challenge lies with obtaining thicker NPLs, to further widen the emission range. This is at present typically achieved via colloidal atomic layer deposition onto CdSe cores, or by synthesizing NPL core/shell structures. Here, we demonstrate a novel reaction scheme, where we start from 4.5 monolayer (ML) NPLs and increase the thickness in a two-step reaction that switches from 2D to 3D growth. The key feature is the enhancement of the growth rate of basal facets by the addition of CdCl2, resulting in a series of nearly monodisperse CdSe NPLs with thicknesses between 5.5 and 8.5 ML. Optical characterization yielded emission peaks from 554 nm up to 625 nm with a line width (fwhm) of 9-13 nm, making them one of the narrowest colloidal nanocrystal emitters currently available in this spectral range. The NPLs maintained a short emission lifetime of 5-11 ns. Finally, due to the increased red shift of the NPL band edge photoluminescence excitation spectra revealed several high-energy peaks. Calculation of the NPL band structure allowed us to identify these excited-state transitions, and spectral shifts are consistent with a significant mixing of light and split-off hole states. Clearly, chloride ions can add a new degree of freedom to the growth of 2D colloidal nanocrystals, yielding new insights into both the NPL synthesis as well as their optoelectronic properties.
123 citations
TL;DR: A new colloidal synthesis method for preparing shape-pure and nearly monodispersed CsPbBr3 nanocubes using secondary amines is reported, which attributes this excellent shape and phase purity to the inability ofsecondary amines to find the right steric conditions at the surface of the NCs, which consequently limits the formation of low-dimensional structures.
Abstract: Fully inorganic cesium lead halide perovskite (CsPbX3) nanocrystals (NCs) have been extensively studied due to their excellent optical properties, especially their high photoluminescence quantum yield (PLQY) and the ease with which the PL can be tuned across the visible spectrum. So far, most strategies for synthesizing CsPbX3 NCs are highly sensitive to the processing conditions and ligand combinations. For example, in the synthesis of nanocubes of different sizes, it is not uncommon to have samples that contain various other shapes, such as nanoplatelets and nanosheets. Here, we report a new colloidal synthesis method for preparing shape-pure and nearly monodispersed CsPbBr3 nanocubes using secondary amines. Regardless of the length of the alkyl chains, the oleic acid concentration, and the reaction temperature, only cube-shaped NCs were obtained. The shape purity and narrow size distribution of the nanocubes are evident from their sharp excitonic features and their ease of self-assembly in superlattices, reaching lateral dimensions of up to 50 μm. We attribute this excellent shape and phase purity to the inability of secondary amines to find the right steric conditions at the surface of the NCs, which consequently limits the formation of low-dimensional structures. Furthermore, no contamination from other phases was observed, not even from Cs4PbBr6, presumably due to the poor ability of secondary aliphatic amines to coordinate to PbBr2 and, hence, to provide a reaction environment that is depleted in Pb.
120 citations
TL;DR: The theoretical model unveils the origin of the catalysttic efficiency of InSe flakes, and correlates the catalytic activity to the Se vacancies at the edge of the flakes.
Abstract: Single- and few-layered InSe flakes are produced by the liquid-phase exfoliation of β-InSe single crystals in 2-propanol, obtaining stable dispersions with a concentration as high as 0.11 g L-1 . Ultracentrifugation is used to tune the morphology, i.e., the lateral size and thickness of the as-produced InSe flakes. It is demonstrated that the obtained InSe flakes have maximum lateral sizes ranging from 30 nm to a few micrometers, and thicknesses ranging from 1 to 20 nm, with a maximum population centered at ≈5 nm, corresponding to 4 Se-In-In-Se quaternary layers. It is also shown that no formation of further InSe-based compounds (such as In2 Se3 ) or oxides occurs during the exfoliation process. The potential of these exfoliated-InSe few-layer flakes as a catalyst for the hydrogen evolution reaction (HER) is tested in hybrid single-walled carbon nanotubes/InSe heterostructures. The dependence of the InSe flakes' morphologies, i.e., surface area and thickness, on the HER performances is highlighted, achieving the best efficiencies with small flakes offering predominant edge effects. The theoretical model unveils the origin of the catalytic efficiency of InSe flakes, and correlates the catalytic activity to the Se vacancies at the edge of the flakes.
93 citations
TL;DR: A new route toward the exploitation of WS2, and possibly other transition-metal dichalcogenides, for the development of next-generation energy-storage devices is demonstrated, thus extending the operating voltage window of conventional WS2-based Li-ion batteries (LIBs).
Abstract: A novel WS2–graphite dual-ion battery (DIB) is developed by combining a conventional graphite cathode and a high-capacity few-layer WS2-flake anode. The WS2 flakes are produced by exploiting wet-jet milling (WJM) exfoliation, which allows large-scale and free-material loss production (i.e., volume up to 8 L h−1 at concentration of 10 g L−1 and exfoliation yield of 100%) of few-layer WS2 flakes in dispersion. The WS2 anodes enable DIBs, based on hexafluorophosphate (PF6–) and lithium (Li+) ions, to achieve charge-specific capacities of 457, 438, 421, 403, 295, and 169 mAh g–1 at current rates of 0.1, 0.2, 0.3, 0.4, 0.8, and 1.0 A g–1, respectively, outperforming conventional DIBs. The WS2-based DIBs operate in the 0 to 4 V cell voltage range, thus extending the operating voltage window of conventional WS2-based Li-ion batteries (LIBs). These results demonstrate a new route toward the exploitation of WS2, and possibly other transition-metal dichalcogenides, for the development of next-generation energy-stor...
87 citations
TL;DR: In this article, a solution-processed PbS quantum dot solar cell, consisting of a PBS-silane functionalized reduced graphene oxide (PbS-rGO) layer on top of the absorber film, was presented.
66 citations
TL;DR: The change in solubility of the NCs induced by the ligand exchange allows for a layer-by-layer deposition process of the DiR films, which yields excellent homogeneity and good thickness control and enables the fabrication of all the LED layers by spin-coating.
Abstract: The surface ligands on colloidal nanocrystals (NCs) play an important role in the performance of NC-based optoelectronic devices such as photovoltaic cells, photodetectors, and light-emitting diodes (LEDs). On one hand, the NC emission depends critically on the passivation of the surface to minimize trap states that can provide nonradiative recombination channels. On the other hand, the electrical properties of NC films are dominated by the ligands that constitute the barriers for charge transport from one NC to its neighbor. Therefore, surface modifications via ligand exchange have been employed to improve the conductance of NC films. However, in LEDs, such surface modifications are more critical because of their possible detrimental effects on the emission properties. In this work, we study the role of surface ligand modifications on the optical and electrical properties of CdSe/CdS dot-in-rods (DiRs) in films and investigate their performance in all-solution-processed LEDs. The DiR films maintain high ...
TL;DR: In this article, a non-noble 3D metal Cl-chemical doping of liquid phase exfoliated single/few-layer flakes of MoSe2 for creating 3d metal oxide-hydr(oxy)oxide hybrid HER-catalysts was reported.
Abstract: Clean hydrogen production through efficient and cost-effective electrochemical water splitting is highly promising to meeting future global energy demands. The design of Earth-abundant materials with both high activity for hydrogen evolution reaction (HER) and electrochemical stability in both acidic and alkaline environments summarize the outcomes needed for practical applications. Here, we report a non-noble 3d metal Cl-chemical doping of liquid phase exfoliated single/few-layer flakes of MoSe2 for creating MoSe2 nanoflakes/3d metal oxide-hydr(oxy)oxide hybrid HER-catalysts. We propose that the electron-transfer from MoSe2 nanoflakes to metal cations and the chlorine complexation-induced both neutralization, as well as the in situ formation of metal oxide-hydr(oxy)oxides on MoSe2 nanoflake's surface, tailor the proton affinity of the derived catalysts, increasing the number and HER-kinetic of their active sites in both acidic and alkaline electrolytes. The electrochemical coupling between the doped-MoSe2 nanoflakes/metal oxide-hydr(oxy)oxide hybrids and single-walled carbon nanotubes heterostructures further accelerates the HER process. Lastly, monolithic stacking of multiple heterostructures is reported as a facile electrode assembly strategy to achieve overpotential for a cathodic current density of 10mAcm-2 of 0.081V and 0.064V in 0.5M H2SO4 and 1M KOH, respectively. This opens up new opportunities to address the current density vs. overpotential requirements targeted in pH-universal H2 production.
TL;DR: The electrochemical performance of industrially produced N-SWCNHs as a sulfur-encapsulating conductive material is explored for the first time using cyclic chronopotentiometry and impedance spectroscopy and the dissolution mechanism of polysulfides inside the electrolyte is explored.
Abstract: Nitrogen-doped single-walled carbon nanohorns (N-SWCNHs) are porous carbon material characterized by unique horn-shape structures with high surface areas and good conductivity. Moreover, they can be mass-produced (tons/year) using a novel proprietary process technology making them an attractive material for various industrial applications. One of the applications is the encapsulation of sulfur, which turns them as promising conductive host materials for lithium–sulfur batteries. Therefore, we explore for the first time the electrochemical performance of industrially produced N-SWCNHs as a sulfur-encapsulating conductive material. Fabrication of lithium–sulfur cells based on N-SWCNHs with sulfur composite could achieve a remarkable initial gravimetric capacity of 1650 mA h g–1, namely equal to 98.5% of the theoretical capacity (1675 mA h g–1), with an exceptional sulfur content as high as 80% in weight. Using cyclic chronopotentiometry and impedance spectroscopy, we also explored the dissolution mechanism ...
TL;DR: In this paper, the photocatalytic and antibacterial activities of PF-co-doped anatase TiO2 nanoparticles (NPs) were studied in details and related to the evolution of their structure and surface composition upon hydrothermal treatment at 250°C for periods up to 12h.
Abstract: Carbapenem-resistant Klebsiella pneumoniae (CP-Kp) is one of the most important opportunistic pathogens strongly associated with nosocomial infections. The capsule of CP-Kp not only contributes to its pathogenic potential but also ensures survival for bacteria in different environments and surfaces. Development of novel reactive nanomaterials can help to inhibit the survival of such microorganism and thereby their spreading in the hospital environment. In this work, the photocatalytic and antibacterial activities of PF-co-doped anatase TiO2 nanoparticles (NPs) were studied in details and related to the evolution of their structure and surface composition upon hydrothermal treatment at 250 °C for periods up to 12 h. Structural and morphological evolution were followed by X-ray diffraction, transmission electron microscopy while the surface composition was studied by X-ray photoelectron spectroscopy. Electron paramagnetic resonance measurements were carried out to reveal the formation of reactive oxygen species (ROS). Both OH and O2 − radicals as well as 1O2 were confirmed and quantitatively compared in different photoirradiated PF-TiO2 NPs dispersions. It was found that hydrothermal treatment increased the photocatalytic and antibacterial activity while PF-co-doping promoted the formation of OH radicals. By the application of PF-co-doping, the elevated level of OH led to rapid inactivation of CP-Kp.
TL;DR: The authors show that the dipole-active phonon resonance of semiconducting nanocrystals can be hybridized by a strongly concentrated terahertz vacuum field of a plasmonic nanocavity, thus achieving strong plasMon–phonon coupling even in the absence of direct teraherstz illumination.
Abstract: Phonons (quanta of collective vibrations) are a major source of energy dissipation and drive some of the most relevant properties of materials. In nanotechnology, phonons severely affect light emission and charge transport of nanodevices. While the phonon response is conventionally considered an inherent property of a nanomaterial, here we show that the dipole-active phonon resonance of semiconducting (CdS) nanocrystals can be drastically reshaped inside a terahertz plasmonic nanocavity, via the phonon strong coupling with the cavity vacuum electric field. Such quantum zero-point field can indeed reach extreme values in a plasmonic nanocavity, thanks to a mode volume well below λ3/107. Through Raman measurements, we find that the nanocrystals within a nanocavity exhibit two new “hybridized” phonon peaks, whose spectral separation increases with the number of nanocrystals. Our findings open exciting perspectives for engineering the optical phonon response of functional nanomaterials and for implementing a novel platform for nanoscale quantum optomechanics. Here the authors show that the dipole-active phonon resonance of semiconducting nanocrystals can be hybridized by a strongly concentrated terahertz vacuum field of a plasmonic nanocavity, thus achieving strong plasmon–phonon coupling even in the absence of direct terahertz illumination.
TL;DR: In this paper, a multibranched fluorinated thiol (BRFT) bearing ultrashort fluorinated alkyl groups, surrounding a hydrocarbon polar core, was used to build omniphobic self-assembled monolayers.
Abstract: Perfluorocarbons (PFCs) have proven to be very efficient in building up omniphobic surfaces because of the peculiar properties of fluorine atoms However, due to their environmental impact and bioaccumulative potential, perfluorinated surfactants with chains longer than six carbon atoms have been banned, and other alternatives had to be found Herein, we demonstrate the possibility to build omniphobic self-assembled monolayers (SAMs) using a multibranched fluorinated thiol (BRFT) bearing ultrashort fluorinated alkyl groups, surrounding a hydrocarbon polar core This unique design allows us to multiply the number of fluorine atoms in the molecule (27 F atoms per molecule), affording a high fluorine density on the surface and a low surface free energy Moreover, the presence of four ether bonds in the core may hasten molecular degradation in the environment because of the cleavage of such bonds in physiological conditions, thus overcoming bioaccumulation issues BRFT may effectively represent a valuable sub
13 Aug 2018
TL;DR: A pH-sensitive drug-delivery system in the form of microparticles, with increased chemotherapeutic action against the osteosarcoma cell line SAOS-2, and with reduced toxicity against the heart myoblastic cell line H9C2 is presented.
Abstract: Osteosarcoma is an aggressive form of bone cancer mostly affecting young people. To date, the most effective strategy for the treatment of osteosarcoma is the surgical removal of the tumor with or ...
TL;DR: In this article, the degradation of MAPI and the subsequent formation of PbI2 at 150 °C were investigated by in situ XRD analysis and showed that this transformation is remarkably slowed down in films coated with trioctyl phosphine oxide and tridodecyl methylammonium iodide.
Abstract: Methylammonium lead iodide (MAPI) has proven to be an exceptional light-absorber for single-junction thin-film solar cells. Nonetheless, degradation induced by environmental agents (air, moisture, heat) limits the stability of this hybrid perovskite. Here, we demonstrate that coating evaporated MAPI thin films with different hydrophobic molecules leads to a significant improvement in their stability. We especially investigated the degradation of MAPI and the subsequent formation of PbI2 at 150 °C by in situ XRD analysis and showed that this transformation is remarkably slowed down in films coated with trioctyl phosphine oxide and tridodecyl methylammonium iodide. This enhances the processability of such films, which is an important aspect for the fabrication of thin-film devices. Eventually, we demonstrate that such protected films can be implemented in single-junction n–i–p solar cells without any loss in the device efficiency.
TL;DR: In this article, the physicochemical properties and the electrochemical performance of a new electrocatalysts for the oxygen reduction reaction (ORR) have been investigated, including the role played by Fe as the active metal.
26 Sep 2018
TL;DR: In this article, a two-step approach to fabricate poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)/cerium oxide (CeO2) nanocomposite fibrous membranes is presented.
Abstract: This study reports a novel two-step approach to fabricate Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)/cerium oxide (CeO2) nanocomposite fibrous membranes. The fabrication method is based on the combination of the electrospinning of the polymer/cerium salt solution and the subsequent in situ thermally activated conversion of the salt in CeO2 nanoparticles, directly in the polymeric fibers. This procedure leads to a homogeneous filler dispersion not only in the bulk of the polymeric fibers, but also on their surface, thus conferring to the system remarkable properties, such as radical scavenging and photo-catalytic activity. These properties are further improved by the decoration of the CeO2 with gold nanoparticles, formed upon the dipping of the solid PVDF-HFP/CeO2 fibers in a gold precursor solution and their subsequent thermal treatment, thanks to the modification of the Ce+3/Ce+4 ratio and the absorption spectrum shifted towards visible wavelengths. Specifically, the presence of Au on th...
TL;DR: It is demonstrated here that the growth from multiple dislocations results in flower-like structures, and the same strategy can be used to produce orthorhombic SnSe nanostructures and nanomaterials.
Abstract: In the present work, we detail a fast and simple solution-based method to synthesize hexagonal SnSe2 nanoplates (NPLs) and their use to produce crystallographically textured SnSe2 nanomaterials. We also demonstrate that the same strategy can be used to produce orthorhombic SnSe nanostructures and nanomaterials. NPLs are grown through a screw dislocation-driven mechanism. This mechanism typically results in pyramidal structures, but we demonstrate here that the growth from multiple dislocations results in flower-like structures. Crystallographically textured SnSe2 bulk nanomaterials obtained from the hot pressing of these SnSe2 structures display highly anisotropic charge and heat transport properties and thermoelectric (TE) figures of merit limited by relatively low electrical conductivities. To improve this parameter, SnSe2 NPLs are blended here with metal nanoparticles. The electrical conductivities of the blends are significantly improved with respect to bare SnSe2 NPLs, what translates into a three-fold increase of the TE Figure of merit, reaching unprecedented ZT values up to 0.65.
TL;DR: In this article, the properties of the new composite material for neural recording and stimulation were assessed and the PEDOT/ox-SWCNH composites were compared with films prepared with one of the most notorious carbonaceous material in this field, the oxidized multi-walled carbon nanotubes (ox-MWCNT).
Abstract: Oxidized single walled carbon nanohorns (ox-SWCNH) were electrodeposited onto gold microelectrode arrays in conjunction with poly(3,4-ethylenedioxythiophene) (PEDOT) and polystirenesulfonate (PSS), and the properties of the new composite material for neural recording and stimulation were assessed. PEDOT/ox-SWCNH composites were compared with films prepared with one of the most notorious carbonaceous material in this field, the oxidized multi-walled Carbon Nanotubes (ox-MWCNT). The PEDOT/ox-SWCNH exhibited superior charge transfer capability, reflecting greater electroactive surface, as confirmed by SEM and EIS characterizations. As a consequence, a charge injection limit of 11.6 mC/cm2 was observed for the new composite, which is higher than the one of PEDOT/ox-MWCNT (8.7 mC/cm2). Having confirmed comparable neural recording performance, the PEDOT/ox-SWCNH composite results very promising for improving therapeutic electrical stimulation in the central and peripheral nervous systems.
TL;DR: The new material, PEDOT-TUDCA, efficiently promoted an electrochemically controlled delivery of the drug, while preserving optimal electrochemical properties, and is a good candidate for prolonging the time span of chronic neural recording brain implants.
Abstract: Localized drug delivery represents one of the most challenging uses of systems based on conductive polymer films. Typically, anionic drugs are incorporated within conductive polymers through electrostatic interaction with the positively charged polymer. Following this approach, the synthetic glucocorticoid dexamethasone phosphate is often delivered from neural probes to reduce the inflammation of the surrounding tissue. In light of the recent literature on the neuroprotective and anti-inflammatory properties of tauroursodeoxycholic acid (TUDCA), for the first time, this natural bile acid was incorporated within poly(3,4-ethylenedioxythiophene) (PEDOT). The new material, PEDOT-TUDCA, efficiently promoted an electrochemically controlled delivery of the drug, while preserving optimal electrochemical properties. Moreover, the low cytotoxicity observed with viability assays, makes PEDOT-TUDCA a good candidate for prolonging the time span of chronic neural recording brain implants.
27 Sep 2018
TL;DR: The electrocatalytic oxygen evolution reaction (OER) is an important half reaction in various technologies, such as metal air batteries and electrochemical water splitting as mentioned in this paper, and it is a half reaction that occurs in transition metal chalcog...
Abstract: The electrocatalytic oxygen evolution reaction (OER) is an important half reaction in various technologies, such as metal air batteries and electrochemical water splitting. Transition metal chalcog...
TL;DR: Density functional theory calculations show that the co-presence of Cu and TiO2 nanoparticles optimizes the free energy of hydrogen adsorption in the final catalyst.
Abstract: We report an interesting case of in situ dynamic nanostructuring of catalyst and support under hydrogen evolution conditions in basic media. When solution-grown CuO nanoplates on titanium substrates are subjected to hydrogen evolution reaction, besides the reduction of CuO to metallic Cu nanoplates, both catalyst and support simultaneously undergo a nanostructuring process. The process is driven by the dissolution–redeposition of Cu and the alkaline etching of the titanium support. The morphology of the resulting nanocomposite material consists of a porous matrix made of ultrasmall Cu nanocrystals and amorphous TiOx nanoparticles. Interestingly, the nanostructuring of the catalyst can be finely controlled by varying the applied potential. Such a process leads to a 5.4-fold improvement in the catalyst activity, which is attributed not only to its large active surface area (formed upon nanostructuring), but also to an improved water dissociation activity, provided by the in situ formation of TiOx nanopartic...
TL;DR: Direct lithography on NC films with e-beams and X-rays has gone through an important development as it has been demonstrated that it can tune further transformations on the NCs, leading to more complex patternings and opening a whole new set of possible applications.
Abstract: In the past couple of decades, colloidal inorganic nanocrystals and, more specifically, semiconductor quantum dots have emerged as crucial materials for the development of nanoscience and nanotechnology, with applications in very diverse areas such as optoelectronics and biotechnology. Films made of inorganic NCs deposited on a substrate can be patterned by e-beam lithography, altering the structure of their capping ligands and thus allowing exposed areas to remain on the substrate while non-exposed areas are redispersed in a solvent, as in a standard lift-off process. This methodology can be described as a direct lithography process, since the exposure is performed directly on the material of interest, in contrast with conventional lithography which uses a polymeric resist as a mask for subsequent material deposition or etching. A few reports from the late 1990 and early 2000 used such direct lithography to fabricate electrical wires from metallic NCs. However, the poor conductivity obtained through this process hindered the widespread use of the technique. In the early 2010, the same method was used to define fluorescent patterns on QD films, allowing for further applications in biosensing. For the past 2 ,3 years, direct lithography on NC films with e-beams and X rays has gone through an important development as it has been demonstrated that it can tune further transformations on the NCs, leading to more complex patternings and opening a whole new set of possible applications.
TL;DR: The smart HSs exhibited good biocompatibility and downregulated GFP production when loaded with anti-GFP siRNA molecules and the high R2 relaxivity values of the HSs suggest their potential as contrast agents in magnetic resonance imaging (MRI) applications.
Abstract: We demonstrate a versatile approach for the preparation of dually responsive smart inorganic heterostructures (HSs) with the potential for exploitation in nanomedicine. We utilize Au–FexOy dimers as templates for generating smart inorganic HSs with a pH-responsive coating and a thermo-responsive coating attached to iron oxide and gold nanoparticles (NPs), respectively. First, a thiol-modified thermo-responsive (PNIPAAM-co-PEGA) polymer could be selectively attached to the gold domain by ligand exchange. The sequential attachment of a catechol-modified initiator to the iron oxide surface enables the in situ polymerization of a pH-responsive (PDMAEA) polymer. As hereby shown, the presence of the two distinct polymer domains on each NP subdomain enables each side of the HS to be loaded with different agents. Indeed, by a gel electrophoresis experiment we demonstrate the loading of siRNA on the pH-responsive polymer and the loading of Nile Blue dye, used as a drug model molecule, on the thermo-responsive polymer. The smart HSs exhibited good biocompatibility and downregulated GFP production when loaded with anti-GFP siRNA molecules. In addition, an investigation of the magnetic relaxivity times revealed that the high R2 relaxivity values of the HSs suggest their potential as contrast agents in magnetic resonance imaging (MRI) applications.
TL;DR: Dexamethasone was successfully integrated into a new electropolymerized PEDOT-Dex composite, leading to a self-adjusting drug release system based on a biochemically hydrolysable bond between dexameth asone and PEDot.
Abstract: PEDOT (Poly(3,4-ethylenedioxythiophene)) is one of the most promising electrode materials for biomedical applications like neural recording and stimulation, thanks to its enhanced biocompatibility and electronic properties. Drug delivery by PEDOT is typically achieved by incorporating drugs as dopants during the electrodeposition procedure and a subsequent release can be promoted by applying a cathodic trigger that reduces PEDOT while enabling the drug to diffuse. This approach has several disadvantages including, for instance, the release of contaminants mainly due to PEDOT decomposition during electrochemical release. Herein we describe a new strategy based on the formation of a chemical linkage between the drug and the conductive polymer. In particular, dexamethasone was successfully integrated into a new electropolymerized PEDOT-Dex composite, leading to a self-adjusting drug release system based on a biochemically hydrolysable bond between dexamethasone and PEDOT.
TL;DR: In this article, the authors used wet chemistry synthesis methods to prepare nanodumbbell structures as a model oxide supported metal catalyst and found that increasing the number of nanocrystals with hollow oxide domains resulted in a decrease in catalytic activity.
Abstract: Using wet chemistry synthesis methods we prepared nanodumbbell structures as a model oxide supported metal catalyst. In this peculiar configuration, a single metallic domain (M) is connected to a single metal oxide (MOx) one. The size, composition and morphology of each domain can be carefully controlled, allowing us to investigate the effects resulting from a hollow morphology of the MOx domains, while all other material’s properties were kept constant. We chose the CO oxidation as a model oxidation reaction and increasing the population of nanocrystals (NCs) with hollow oxide domains resulted in a decrease in catalytic activity. Despite the manipulation of oxide morphology affected the surface charge of the Au domain, the bulk oxide reducibility and the crystallinity of the nanosized oxide support, the rate limiting step of CO oxidation was not affected. The same apparent activation energy was indeed measured independently from the population of NCs with hollow oxide domains. The difference in catalytic performance was thus ascribed to a different number of interfacial active sites when the morphology evolved from full to hollow.
TL;DR: Spectroscopic experiments confirm the formation of the intercluster network and reveal the permanent nature of their excimer-like behavior, thus extending the potential impact and applicability of metal cluster superstructures as efficient and stable non-resonant single-particle emitters.
Abstract: Metal clusters with appropriate molecular ligands have been shown to be suitable subnanometer building blocks for supramolecular architectures with controlled secondary interactions, providing access to physical regimes not achievable with conventional intermolecular motifs. An example is the excimer photophysics exhibited by individual cluster-based superstructures produced by top-down etching of gold nanoparticles. Now, a supramolecular architecture of copper clusters is presented with controlled optical properties and efficient non-resonant luminescence produced via a novel bottom-up synthesis using mild green reductants followed by a ligand exchange reaction and spontaneous supramolecular assembly. Spectroscopic experiments confirm the formation of the intercluster network and reveal the permanent nature of their excimer-like behavior, thus extending the potential impact and applicability of metal cluster superstructures as efficient and stable non-resonant single-particle emitters.