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1.
Nat Commun ; 11(1): 3611, 2020 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-32681047

RESUMO

Temperature measurement at the nanoscale is of paramount importance in the fields of nanoscience and nanotechnology, and calls for the development of versatile, high-resolution thermometry techniques. Here, the working principle and quantitative performance of a cost-effective nanothermometer are experimentally demonstrated, using a molecular spin-crossover thin film as a surface temperature sensor, probed optically. We evidence highly reliable thermometric performance (diffraction-limited sub-µm spatial, µs temporal and 1 °C thermal resolution), which stems to a large extent from the unprecedented quality of the vacuum-deposited thin films of the molecular complex [Fe(HB(1,2,4-triazol-1-yl)3)2] used in this work, in terms of fabrication and switching endurance (>107 thermal cycles in ambient air). As such, our results not only afford for a fully-fledged nanothermometry method, but set also a forthcoming stage in spin-crossover research, which has awaited, since the visionary ideas of Olivier Kahn in the 90's, a real-world, technological application.

2.
Artigo em Inglês | MEDLINE | ID: mdl-32666596

RESUMO

We report a series of meltable Fe II complexes, which, depending on the length of aliphatic chains, display abrupt "forward" low-spin to high-spin transition or unprecedented melting-triggered "reverse" high-spin to low-spin transition on temperature rise. The "reverse spin transition" is perfectly reproducible on thermal cycling and the obtained materials are easily processable in the form of thin film due to soft matter nature. We found that the discovered approach represents a potentially generalizable new avenue to control both the location in temperature and the direction of the spin transition in meltable compounds.

3.
Artigo em Inglês | MEDLINE | ID: mdl-32466653

RESUMO

In this work, scanning probe microscopies (SPMs) are used for the analysis of PBDB-T, ITIC, and PBDB-T:ITIC layers of solar cells (OSCs). Scanning tunneling microscopy (STM) images of PBDB-T reveal that thin films (<1 nm) tend to form worm-like pattern (amorphous type) domains with an average chain-to-chain distance of 950 pm; likewise, STM images of ITIC show that side arms form chain-like patterns. STM images of PBDB-T:ITIC blend suggest why PBDB-T domains could facilitate charge dissociation. Further, a strong interchain π-π interaction of the ITIC molecules could promote self-organization, and under the mutual interaction with the PBDB-T polymer, it could influence the pathway formation for electron transport. Moreover, when correlating electrostatic force microscopy (EFM) and photoconductive atomic force microscopy (pc-AFM), the blend morphology and its electrical/electronic properties are determined; the ideal domain size of PBDB-T:ITIC blend phases for maximizing the generated photocurrent is 15-35 nm. Furthermore, phase contrast and surface electric potential characteristics with Kelvin probe force microscopy (KPFM) are measured to examine additional details about the surface and potential changes due to the domain differences in the active layer. OSCs based on the nonfullerene PBDB-T:ITIC active layer reach an average power conversion efficiency (PCE) of 9.1% (best 9.2%).

4.
Nanoscale ; 2020 Apr 05.
Artigo em Inglês | MEDLINE | ID: mdl-32248213

RESUMO

A main goal of molecular electronics is to relate the performance of devices to the structure and electronic state of molecules. Among the variety of possibilities that organic, organometallic and coordination chemistries offer to tune the energy levels of molecular components, spin crossover phenomenon is a perfect candidate for elaboration of molecular switches. The reorganization of the electronic state population of the molecules associated to the spin crossover can indeed lead to a significant change in conductivity. However, molecular spin crossover is very sensitive to the environment and can disappear once the molecules are integrated into devices. Here, we show that the association of ultra-small 1.2 nm platinum nanoparticles with FeII triazole-based spin crossover coordination polymers leads to self-assemblies, extremely well organized at the sub-3 nm scale. The quasi-perfect alignment of nanoparticles observed by transmission electron microscopy, in addition to specific signature in infrared spectroscopy, demonstrates the coordination of the long-chain molecules with the nanoparticles. Spin crossover is confirmed in such assemblies by X-ray absorption spectroscopic measurements and shows unambiguous characteristics both in magnetic and charge transport measurements. Coordinating polymers are therefore ideal candidates for the elaboration of robust, well-organized, hybrid self-assemblies with metallic nanoparticles, while maintaining sensitive functional properties, such as spin crossover.

5.
Adv Mater ; : e2000987, 2020 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-32301210

RESUMO

The thermally induced spin-crossover (SCO) phenomenon in transition metal complexes is an entropy-driven process, which has been extensively studied through calorimetric methods. Yet, the excess heat capacity associated with the molecular spin-state switching has never been explored for practical applications. Herein, the thermal damping effect of an SCO film is experimentally assessed by monitoring the transient heating response of SCO-coated metallic microwires, Joule-heated by current pulses. A damping of the wire temperature, up to 10%, is evidenced on a time scale of tens of microseconds due to the spin-state switching of the molecular film. Fast heat-charging dynamics and negligible fatigability are demonstrated, which, together with the solid-solid nature of the spin transition, appear as promising features for achieving thermal energy management applications in functional devices.

6.
J Phys Condens Matter ; 32(26): 264002, 2020 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-32120350

RESUMO

The complex dielectric permittivity of a series of spin crossover complexes, with variable ligand stoichiometry [Fe(Htrz)1+y-x (trz)2-y (NH2trz) x ](BF4) y ·nH2O, has been investigated as a function of temperature in a wide frequency range. In each compound, a substantial drop of the conductivity and permittivity is evidenced when going from the low spin to the high spin state, albeit with decreasing amplitude for increasing ligand substitution (i.e. for increasing x). The deconvolution of the dielectric spectra using the Havriliak-Negami equation allowed to extract the dipole and conductivity relaxation times, their distributions as well as the dielectric strengths in both spin states. Remarkably, no clear correlation appears between the conductivity changes and the lattice properties (Debye temperature) in the dilution series. We rationalize these results by considering the dimensionality of the system (1D), wherein the charge transport occurs most likely by hopping along the [Fe(Rtrz)3] n n+ chains.

7.
EMBO Mol Med ; 12(3): e11421, 2020 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-32072760

RESUMO

Genomic data sharing is becoming more important as scientists join forces across borders in biomedical research for the benefit of patients and society. The EU's General Data Protection Regulation (GDPR) helps simplify sharing of such data at the European and international level. However, initial optimism has dried up as EU member states go their own ways in implementing the GDPR into national laws, and as legal cases challenging data sharing reach courts. Codes of conduct could facilitate data sharing in Europe and better connect it to global health research. This commentary explains the potential of codes of conduct for addressees and drafters. Codes are no panacea though; other measures may be necessary to ensure that Europe remains collaborative and competitive in biomedical research. Nevertheless, codes of conduct would bring immediate benefits and, in the long term, could foster a true European ecosystem for joint biomedical research and easier international data sharing.

8.
J Phys Condens Matter ; 32(21): 214010, 2020 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-32032965

RESUMO

Multilayer crossbar junctions composed of ITO/[Fe(HB(1,2,4-triazol-1-yl)3)2]/M (with M = Al or Ca) were fabricated and investigated for their resistance switching properties. Current-voltage-temperature maps revealed ON/OFF resistance ratios as high as 400, with the ON and OFF states defined, respectively, as the low-resistance, low spin state and the high-resistance, high spin state of the spin crossover layer. Similar results were obtained with Al and Ca cathodes indicating that the charge transport in the insulating spin crossover film is at the origin of the resistance switching instead of electron injection at the electrodes. The reproducibility and stability of the device properties were also studied.

10.
Elife ; 92020 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-31916939

RESUMO

Inhibitory autapses are self-innervating synaptic connections in GABAergic interneurons in the brain. Autapses in neocortical layers have not been systematically investigated, and their function in different mammalian species and specific interneuron types is poorly known. We investigated GABAergic parvalbumin-expressing basket cells (pvBCs) in layer 2/3 (L2/3) in human neocortical tissue resected in deep-brain surgery, and in mice as control. Most pvBCs showed robust GABAAR-mediated self-innervation in both species, but autapses were rare in nonfast-spiking GABAergic interneurons. Light- and electron microscopy analyses revealed pvBC axons innervating their own soma and proximal dendrites. GABAergic self-inhibition conductance was similar in human and mouse pvBCs and comparable to that of synapses from pvBCs to other L2/3 neurons. Autaptic conductance prolonged somatic inhibition in pvBCs after a spike and inhibited repetitive firing. Perisomatic autaptic inhibition is common in both human and mouse pvBCs of supragranular neocortex, where they efficiently control discharge of the pvBCs.

11.
Science ; 367(6477): 528-537, 2020 01 31.
Artigo em Inglês | MEDLINE | ID: mdl-31831638

RESUMO

Microglia are the main immune cells in the brain and have roles in brain homeostasis and neurological diseases. Mechanisms underlying microglia-neuron communication remain elusive. Here, we identified an interaction site between neuronal cell bodies and microglial processes in mouse and human brain. Somatic microglia-neuron junctions have a specialized nanoarchitecture optimized for purinergic signaling. Activity of neuronal mitochondria was linked with microglial junction formation, which was induced rapidly in response to neuronal activation and blocked by inhibition of P2Y12 receptors. Brain injury-induced changes at somatic junctions triggered P2Y12 receptor-dependent microglial neuroprotection, regulating neuronal calcium load and functional connectivity. Thus, microglial processes at these junctions could potentially monitor and protect neuronal functions.


Assuntos
Lesões Encefálicas/imunologia , Encéfalo/imunologia , Junções Intercelulares/imunologia , Microglia/imunologia , Neurônios/imunologia , Receptores Purinérgicos P2Y12/fisiologia , Animais , Encéfalo/ultraestrutura , Lesões Encefálicas/patologia , Cálcio , Comunicação Celular/imunologia , Células HEK293 , Humanos , Camundongos , Mitocôndrias/imunologia , Canais de Potássio Shab/genética , Canais de Potássio Shab/fisiologia , Transdução de Sinais
12.
J Empir Res Hum Res Ethics ; : 1556264619887073, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31729900

RESUMO

Dynamic consent (DC) is an approach to consent that enables people, through an interactive digital interface, to make granular decisions about their ongoing participation. This approach has been explored within biomedical research, in fields such as biobanking and genomics, where ongoing contact is required with participants. It is posited that DC can enhance decisional autonomy and improve researcher-participant communication. Currently, there is a lack of evidence about the measurable effects of DC-based tools. This article outlines a framework for DC evaluation and reporting. The article draws upon the evidence for enhanced modes of informed consent for research as the basis for a logic model. It outlines how future evaluations of DC should be designed to maximize their quality, replicability, and relevance based on this framework. Finally, the article considers best-practice for reporting studies that assess DC, to enable future research and implementation to build upon the emerging evidence base.

13.
J Phys Chem Lett ; 10(23): 7391-7396, 2019 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-31714791

RESUMO

We use broad-band dielectric spectroscopy to investigate the spin-state dependence of electrical properties of the [Fe(Htrz)2(trz)](BF4) spin crossover complex. We show that the Havriliak-Negami theory can fully describe the variation of the complex dielectric permittivity of the material across the pressure-temperature phase diagram. The analysis reveals three dielectric relaxation processes, which we attribute to electrode/interface polarization, dipole relaxation, and charge transport relaxation. The contribution of the latter appears significant to the dielectric strength. Remarkably, the permittivity and conductivity changes between the high spin and low spin states are amplified at the corresponding relaxation frequencies.

14.
Small ; 15(47): e1903892, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31617319

RESUMO

Thin films of the molecular spin-crossover complex [Fe(HB(1,2,4-triazol-1-yl)3 )2 ] undergo spin transition above room temperature, which can be exploited in sensors, actuators, and information processing devices. Variable temperature viscoelastic mapping of the films by atomic force microscopy reveals a pronounced decrease of the elastic modulus when going from the low spin (5.2 ± 0.4 GPa) to the high spin (3.6 ± 0.2 GPa) state, which is also accompanied by increasing energy dissipation. This technique allows imaging, with high spatial resolution, of the formation of high spin puddles around film defects, which is ascribed to local strain relaxation. On the other hand, no clustering process due to cooperative phenomena was observed. This experimental approach sets the stage for the investigation of spin transition at the nanoscale, including phase nucleation and evolution as well as local strain effects.

15.
BMC Med Ethics ; 20(1): 55, 2019 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-31370847

RESUMO

BACKGROUND: Rare Disease research has seen tremendous advancements over the last decades, with the development of new technologies, various global collaborative efforts and improved data sharing. To maximize the impact of and to further build on these developments, there is a need for model consent clauses for rare diseases research, in order to improve data interoperability, to meet the informational needs of participants, and to ensure proper ethical and legal use of data sources and participants' overall protection. METHODS: A global Task Force was set up to develop model consent clauses specific to rare diseases research, that are comprehensive, harmonized, readily accessible, and internationally applicable, facilitating the recruitment and consent of rare disease research participants around the world. Existing consent forms and notices of consent were analyzed and classified under different consent themes, which were used as background to develop the model consent clauses. RESULTS: The IRDiRC-GA4GH MCC Task Force met in September 2018, to discuss and design model consent clauses. Based on analyzed consent forms, they listed generic core elements and designed the following rare disease research specific core elements; Rare Disease Research Introductory Clause, Familial Participation, Audio/Visual Imaging, Collecting, storing, sharing of rare disease data, Recontact for matching, Data Linkage, Return of Results to Family Members, Incapacity/Death, and Benefits. CONCLUSION: The model consent clauses presented in this article have been drafted to highlight consent elements that bear in mind the trends in rare disease research, while providing a tool to help foster harmonization and collaborative efforts.


Assuntos
Pesquisa Biomédica/ética , Termos de Consentimento/normas , Consentimento Livre e Esclarecido/normas , Doenças Raras/terapia , Pesquisa Biomédica/métodos , Pesquisa Biomédica/normas , Termos de Consentimento/ética , Humanos , Consentimento Livre e Esclarecido/ética
16.
Adv Mater ; 31(25): e1901361, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31034107

RESUMO

Using ultrafast optical absorption spectroscopy, the room-temperature spin-state switching dynamics induced by a femtosecond laser pulse in high-quality thin films of the molecular spin-crossover (SCO) complex [Fe(HB(tz)3 )2 ] (tz = 1,2,4-triazol-1-yl) are studied. These measurements reveal that the early, sub-picosecond, low-spin to high-spin photoswitching event, with linear response to the laser pulse energy, can be followed under certain conditions by a second switching process occurring on a timescale of tens of nanoseconds, enabling nonlinear amplification. This out-of-equilibrium dynamics is discussed in light of the characteristic timescales associated with the different switching mechanisms, i.e., the electronic and structural rearrangements of photoexcited molecules, the propagation of strain waves at the material scale, and the thermal activation above the molecular energy barrier. Importantly, the additional, nonlinear switching step appears to be completely suppressed in the thinnest (50 nm) film due to the efficient heat transfer to the substrate, allowing the system to retrieve the thermal equilibrium state on the 100 ns timescale. These results provide a first milestone toward the assessment of the physical parameters that drive the photoresponse of SCO thin films, opening up appealing perspectives for their use as high-frequency all-optical switches working at room temperature.

17.
Chem Commun (Camb) ; 55(33): 4769-4772, 2019 Apr 18.
Artigo em Inglês | MEDLINE | ID: mdl-30924832

RESUMO

A series of spin-crossover (SCO) coordination nanoparticles (ca. 60 nm) with the general formulae [Fe(Htrz)1+y-x(trz)2-y(NH2trz)x](BF4)y·nH2O (x = 0, 0.1, 0.2 and 0.3) were synthesized in concentrated solutions without using any surfactant or polymer. The nanoparticle powders were investigated by transmission electron microscopy, powder X-ray diffraction, magnetometry, calorimetry, Raman/IR spectroscopies, elemental analysis and 57Fe Mössbauer spectrometry. Remarkably, the latter revealed a large decrease of the lattice stiffness when incorporating a small amount of amino-triazole ligand, reflected by the drop of the Debye temperature from 285 K (x = 0) to 205 K (x = 0.3). This collapse of the lattice cohesion was attributed to a reorganization of the supramolecular interactions between the Fe-triazole chains. This effect on the SCO properties is also discussed.

18.
J Phys Chem Lett ; 10(7): 1511-1515, 2019 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-30883126

RESUMO

Spin-crossover nanomaterials have been actively studied in the past decade for their potential technological applications in sensing, actuating, and information processing devices. Unfortunately, an increasing number of the metallic centers become inactive at reduced sizes, presumably due to surface effects, limiting their switching ability and thus the scope of applications. Here we report on the investigation of "frozen" metallic centers in nanoparticles (2-80 nm size) of the spin-crossover compound Fe(pyrazine)[Ni(CN)4]. Magnetic measurements reveal both high-spin and low-spin residual fractions at atmospheric pressure. A pressure-induced transition of the high-spin residue is observed at around 1.5 GPa by synchrotron Mössbauer spectroscopy. We show that it is equivalent to a downshift of the transition temperature by ca. 400 K due to the size reduction. Unexpectedly, small-angle neutron scattering experiments demonstrate that these high-spin residual centers are not confined to the surface, which contradicts general theoretical considerations.

19.
Diabetologia ; 62(4): 717-725, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30637442

RESUMO

AIMS/HYPOTHESIS: Glucagon-like peptide 1 (GLP-1) receptors are expressed by pancreatic beta cells and GLP-1 receptor signalling promotes insulin secretion. GLP-1 receptor agonists have neural effects and are therapeutically promising for mild cognitive impairment and Alzheimer's disease. Our previous results showed that insulin is released by neurogliaform neurons in the cerebral cortex, but the expression of GLP-1 receptors on insulin-producing neocortical neurons has not been tested. In this study, we aimed to determine whether GLP-1 receptors are present in insulin-containing neurons. METHODS: We harvested the cytoplasm of electrophysiologically and anatomically identified neurogliaform interneurons during patch-clamp recordings performed in slices of rat neocortex. Using single-cell digital PCR, we determined copy numbers of Glp1r mRNA and other key genes in neurogliaform cells harvested in conditions corresponding to hypoglycaemia (0.5 mmol/l glucose) and hyperglycaemia (10 mmol/l glucose). In addition, we performed whole-cell patch-clamp recordings on neurogliaform cells to test the effects of GLP-1 receptor agonists for functional validation of single-cell digital PCR results. RESULTS: Single-cell digital PCR revealed GLP-1 receptor expression in neurogliaform cells and showed that copy numbers of mRNA of the Glp1r gene in hyperglycaemia exceeded those in hypoglycaemia by 9.6 times (p < 0.008). Moreover, single-cell digital PCR confirmed co-expression of Glp1r and Ins2 mRNA in neurogliaform cells. Functional expression of GLP-1 receptors was confirmed with whole-cell patch-clamp electrophysiology, showing a reversible effect of GLP-1 on neurogliaform cells. This effect was prevented by pre-treatment with the GLP-1 receptor-specific antagonist exendin-3(9-39) and was absent in hypoglycaemia. In addition, single-cell digital PCR of neurogliaform cells revealed that the expression of transcription factors (Pdx1, Isl1, Mafb) are important in beta cell development. CONCLUSIONS/INTERPRETATION: Our results provide evidence for the functional expression of GLP-1 receptors in neurons known to release insulin in the cerebral cortex. Hyperglycaemia increases the expression of GLP-1 receptors in neurogliaform cells, suggesting that endogenous incretins and therapeutic GLP-1 receptor agonists might have effects on these neurons, similar to those in pancreatic beta cells.


Assuntos
Córtex Cerebral/metabolismo , Receptor do Peptídeo Semelhante ao Glucagon 1/metabolismo , Insulina/metabolismo , Interneurônios/metabolismo , Animais , Citoplasma/metabolismo , Peptídeo 1 Semelhante ao Glucagon/metabolismo , Hiperglicemia/metabolismo , Hipoglicemia/metabolismo , Masculino , Neocórtex/metabolismo , Ratos , Ratos Wistar , Transdução de Sinais
20.
Angew Chem Int Ed Engl ; 57(45): 14758-14763, 2018 11 05.
Artigo em Inglês | MEDLINE | ID: mdl-30230674

RESUMO

Despite stated in some highly cited articles, magnetite is devoided of peroxidase activity. In fact, this very stable mixed valence FeII O⋅FeIII 2 O3 complex is not catalytically competent to oxidize standard peroxidase substrates, especially at the biologically relevant pH value of 7.4. In addition, magnetite whose deleterious redox activity has been suspected in Alzheimer's disease brain damages, does not significantly interact with amyloid peptide Aß in vitro, and is not able to induce, either in the presence or absence of Aß, the reductive activation of dioxygen, the first step of an oxidative stress. In fact, this highly insoluble mineral iron derivative is probably not involved in the oxidative damage of brain neurons of patients with AD.


Assuntos
Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , Óxido Ferroso-Férrico/metabolismo , Estresse Oxidativo , Amiloide/metabolismo , Encéfalo/metabolismo , Humanos , Peroxidase/metabolismo
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