Carbon Nano-onions: Potassium Intercalation and Reductive Covalent Functionalization.

Herein we report the synthesis of covalently functionalized carbon nano-onions (CNOs) via a reductive approach using unprecedented alkali-metal CNO intercalation compounds. For the first time, an in situ Raman study of the controlled intercalation process with potassium has been carried out revealing a Fano resonance in highly doped CNOs. The intercalation was further confirmed by electron energy loss spectroscopy and X-ray diffraction. Moreover, the experimental results have been rationalized with DFT calculations. Covalently functionalized CNO derivatives were synthesized by using phenyl iodide and n-hexyl iodide as electrophiles in model nucleophilic substitution reactions. The functionalized CNOs were exhaustively characterized by statistical Raman spectroscopy, thermogravimetric analysis coupled with gas chromatography and mass spectrometry, dynamic light scattering, UV-vis, and ATR-FTIR spectroscopies. This work provides important insights into the understanding of the basic principles of reductive CNOs functionalization and will pave the way for the use of CNOs in a wide range of potential applications, such as energy storage, photovoltaics, or molecular electronics.

Understanding the Electron-Doping Mechanism in Potassium-Intercalated Single-Walled Carbon Nanotubes.

Single-walled carbon nanotubes (SWCNTs) can be doped with potassium, similar to graphite, leading to intercalation compounds. These binary systems exhibit a clear metallic character. However, the entire picture of how electron doping (e-doping) modifies the SWCNTs' vibrational spectra as a function of their diameter, chirality, and metallicity is still elusive. Herein, we present a detailed study of the intercalation and solid state reduction of metallic and semiconducting enriched HiPco SWCNTs. We performed a combined experimental and theoretical study of the evolution of their Raman response with potassium exposure, focusing specifically on their radial breathing mode (RBM). We found the charge donated from the potassium atoms occupies antibonding π orbitals of the SWCNTs, weakening their C-C bonds, and reducing the RBM frequency. This RBM downshift with increasing doping level is quasi-linear with a steplike behavior when the Fermi level crosses a van Hove singularity for semiconducting species. Moreover, this weakening of the C-C bonds is greater with decreasing curvature, or increasing diameter. Overall, this suggests the RBM downshift with e-doping is proportional to both the SWCNT's integrated density of states (DOS) ϱ(ε) and diameter d. We have provided a precise and complete description of the complex electron doping mechanism in SWCNTs up to a charge density of -18 me/C, far beyond that achievable by standard gate voltage studies, not being the highest doping possible, but high enough to track the effects of doping in SWCNTs based on their excitation energy, diameter, band gap energy, chiral angle, and metallicity. This work is highly relevant to tuning the electronic properties of SWCNTs for applications in nanoelectronics, plasmonics, and thermoelectricity.

Neuronal TDP-43 depletion affects activity-dependent plasticity.

TAR DNA-binding protein 43 (TDP-43) is a hallmark of some neurodegenerative disorders, such as frontotemporal lobar degeneration and amyotrophic lateral sclerosis. TDP-43-related pathology is characterized by its abnormally phosphorylated and ubiquitinated aggregates. It is involved in many aspects of RNA processing, including mRNA splicing, transport, and translation. However, its exact physiological function and role in mechanisms that lead to neuronal degeneration remain elusive. Transgenic rats that were characterized by TDP-43 depletion in neurons exhibited enhancement of the acquisition of fear memory. At the cellular level, TDP-43-depleted neurons exhibited a decrease in the short-term plasticity of intrinsic neuronal excitability. The induction of long-term potentiation in the CA3-CA1 areas of the hippocampus resulted in more stable synaptic enhancement. At the molecular level, the protein levels of an unedited (R) FLOP variant of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) GluR1 and GluR2/3 subunits decreased in the hippocampus. Alterations of FLOP/FLIP subunit composition affected AMPAR kinetics, reflected by cyclothiazide-dependent slowing of the decay time of AMPAR-mediated miniature excitatory postsynaptic currents. These findings suggest that TDP-43 may regulate activity-dependent neuronal plasticity, possibly by regulating the splicing of genes that are responsible for fast synaptic transmission and membrane potential.

Effect of Spin Multiplicity in O2 Adsorption and Dissociation on Small Bimetallic AuAg Clusters.

To dispose of atomic oxygen, it is necessary the O2 activation; however, an energy barrier must be overcome to break the O-O bond. This work presents theoretical calculations of the O2 adsorption and dissociation on small pure Aun and Agm and bimetallic AunAgm (n + m ≤ 6) clusters using the density functional theory (DFT) and the zeroth-order regular approximation (ZORA) to explicitly include scalar relativistic effects. The most stable AunAgm clusters contain a higher concentration of Au with Ag atoms located in the center of the cluster. The O2 adsorption energy on pure and bimetallic clusters and the ensuing geometries depend on the spin multiplicity of the system. For a doublet multiplicity, O2 is adsorbed in a bridge configuration, whereas for a triplet only one O-metal bond is formed. The charge transfer from metal toward O2 occupies the σ*O-O antibonding natural bond orbital, which weakens the oxygen bond. The Au3 (2A) cluster presents the lowest activation energy to dissociate O2, whereas the opposite applies to the AuAg (3A) system. In the O2 activation, bimetallic clusters are not as active as pure Aun clusters due to the charge donated by Ag atoms being shared between O2 and Au atoms.

Exploring the Formation of Black Phosphorus Intercalation Compounds with Alkali Metals.

Black phosphorus intercalation compounds (BPICs) with alkali metals (namely: K and Na) have been synthesized in bulk by solid-state as well as vapor-phase reactions. By means of a combination of in situ X-ray diffraction, Raman spectroscopy, and DFT calculations the structural behavior of the BPICs at different intercalation stages has been demonstrated for the first time. Our results provide a glimpse into the very first steps of a new family of intercalation compounds, with a distinct behavior as compared to its graphite analogues (GICs), showing a remarkable structural complexity and a dynamic behavior.

Photochemical Optimization of a Silver Nanoprism/Graphene Oxide Nanocomposite's Antibacterial Properties.

Optimizing the antibacterial properties of nanocomposites is a fundamental challenge for many biomedical applications. Here, we study how we may optimize the antibacterial activity of narrow-sized anisotropically flat silver nanoprisms (S-NPs) on graphene oxide (GO) against Escherichia coli. To do so, we transformed silver nanoparticles (AgNPs) into S-NPs and anchored them to GO via a facile and low-cost photochemical reduction method by varying the irradiation wavelength during the synthesis process in the visible range (440 to 650 nm and white light). We performed a physicochemical characterization of the resulting S-NP/GO nanocomposite using a combination of UV-vis spectroscopy, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Our results reveal a synergistic effect between the silver nanoprism and the oxygen functional groups of the GO surface. The antibacterial activity of the S-NPs/GO nanocomposite shows a significantly higher 53% inhibition efficiency after being irradiated with a 540 nm wavelength light source, compared to AgNPs with a 1% inhibition efficiency, respectively. In so doing, we have demonstrated the utility of a low-cost photoreduction method to control the structural properties of silver nanoprism on GO and, in this way, enhance the antibacterial properties of the nanocomposite. These results should be of great interest in a wide range of biomedical applications and medical devices.

Infra-Red Active Dirac Plasmon Serie in Potassium Doped-Graphene (KC8) Nanoribbons Array on Al2O3 Substrate.

A theoretical formulation of the electromagnetic response in graphene ribbons on dielectric substrate is derived in the framework of the ab initio method. The formulation is applied to calculate the electromagnetic energy absorption in an array of potassium-doped graphene nanoribbons (KC8-NR) deposited on a dielectric Al2O3 substrate. It is demonstrated that the replacement of the flat KC8 by an array of KC8-NR transforms the Drude tail in the absorption spectra into a series of infrared-active Dirac plasmon resonances. It is also shown that the series of Dirac plasmon resonances, when unfolded across the extended Brillouin zones, resembles the Dirac plasmon. The Dirac plasmon resonances' band structure, within the first Brillouin zone, is calculated. Finally, an excellent agreement between the theoretical absorption and recent experimental results for differential transmission through graphene on an SiO2/Si surface is presented. The theoretically predicted micrometer graphene nanoribbons intercalation compound (GNRIC) in a stage-I-like KC8 is confirmed to be synthesized for Dirac plasmon resonances.

Optimized and scalable synthesis of magnetic nanoparticles for RNA extraction in response to developing countries' needs in the detection and control of SARS-CoV-2.

Ecuador is one of the most affected countries, with the coronavirus disease 2019 (COVID-19) infection, in Latin America derived from an ongoing economic crisis. One of the most important methods for COVID-19 detection is the use of techniques such as real time RT-PCR based on a previous extraction/purification of RNA procedure from nasopharyngeal cells using functionalized magnetic nanoparticles (MNP). This technique allows the processing of ~ 10,000 tests per day in private companies and around hundreds per day at local Universities guaranteeing to reach a wide range of the population. However, the main drawback of this method is the need for specialized MNP with a strong negative charge for the viral RNA extraction to detect the existence of the SARS-CoV-2 virus. Here we present a simplified low cost method to produce 10 g of nanoparticles in 100 mL of solution that was scaled to one litter by parallelizing the process 10 times in just two days and allowing for the possibility of making ~ 50,000 COVID-19 tests. This communication helps in reducing the cost of acquiring MNP for diverse biomolecular applications supporting developing country budgets constraints and chemical availability specially during the COVID-19 International Health Emergency.

[Diabetic foot attack. Pathophysiological description, clinical presentation, treatment and outcomes]. / Ataque de pie diabético. Descripción fisiopatológica, presentación clínica, tratamiento y evolución.

Diabetic foot attack has an acute and severe presentation that threatens the affected limb and the patient's life. It is a term that arises from the need to identify those patients that require urgent intervention; it conveys a sense of urgency and severity, reminding the term of "time is tissue". The classic presentation is that of a severe infected foot with rapidly progressive necrosis that requires urgent surgery to debride all necrotic tissue and purulent collections, providing an adequate antibiotic treatment. Ischemic diabetic foot attack that demands urgent revascularization and the acute Charcot neuroarthropathy for which primacy is given to diagnostic confirmation and off-loading are also consid ered atypical presentations of diabetic foot attack. The aim of identifying these diabetic foot presentations is to promote rapid intervention to provide adequate and effective treatment, avoiding the most feared complication which is the limb amputation. In the present review, a description of the pathophysiology, clinical presentation, treatment and evolution of the three types of diabetic foot attack is made.

El ataque de pie diabético tiene una presentación aguda y grave que representa una amenaza para la conservación del miembro afectado e incluso para la vida del paciente. Es un término que surge por la necesidad de facilitar la identificación de aquellos pacientes que requieren intervención urgente, dándole un sentido de urgencia y gravedad, reforzando el concepto de que "tiempo es tejido". Se han identificado tres situaciones en las cuales urge este tipo de intervención: el ataque de pie diabético infectado, donde el pie se presenta con una infección grave y con rápida progresión de necrosis que requiere internación, un desbridamiento rápido de tejido desvitalizado, drenaje de colecciones y tratamiento antibiótico; el ataque de pie diabético isquémico que implica isquemia progresiva y evolutiva y requiere revascularización urgente, y la neuroartropatía de Charcot en fase aguda que demanda rápida identificación y descarga. El reconocimiento oportuno de dichas presentaciones es fundamental para iniciar un tratamiento adecuado y mejorar la evolución de los pacientes. En la presente revisión, se realiza una descripción de la fisiopatología, presentación clínica, tratamiento y evolución de los tres tipos de ataque de pie diabético.

Ultralong Spin Lifetime in Light Alkali Atom Doped Graphene.

Today's great challenges of energy and informational technologies are addressed with a singular compound, Li- and Na-doped few-layer graphene. All that is impossible for graphite (homogeneous and high-level Na doping) and unstable for single-layer graphene works very well for this structure. The transformation of the Raman G line to a Fano line shape and the emergence of strong, metallic-like electron spin resonance (ESR) modes attest the high level of graphene doping in liquid ammonia for both kinds of alkali atoms. The spin-relaxation time in our materials, deduced from the ESR line width, is 6-8 ns, which is comparable to the longest values found in spin-transport experiments on ultrahigh-mobility graphene flakes. This could qualify our material as a promising candidate in spintronics devices. On the other hand, the successful sodium doping, this being a highly abundant metal, could be an encouraging alternative to lithium batteries.

Characterizing the maximum number of layers in chemically exfoliated graphene.

An efficient route to synthesize macroscopic amounts of graphene is highly desired and bulk characterization of such samples, in terms of the number of layers, is equally important. We present a Raman spectroscopy-based method to determine the typical upper limit of the number of graphene layers in chemically exfoliated graphene. We utilize a controlled vapour-phase potassium intercalation technique and identify a lightly doped stage, where the Raman modes of undoped and doped few-layer graphene flakes coexist. The spectra can be unambiguously distinguished from alkali doped graphite, and modeling with the typical upper limit of the layers yields an upper limit of flake thickness of five layers with a significant single-layer graphene content. Complementary statistical AFM measurements on individual few-layer graphene flakes find a consistent distribution of the layer numbers.

Precise determination of graphene functionalization by in situ Raman spectroscopy.

The verification of a successful covalent functionalization of graphene and related carbon allotropes can easily be carried out by Raman spectroscopy. Nevertheless, the unequivocal assignment and resolution of individual lattice modes associated with the covalent binding of addends was elusive up to now. Here we present an in situ Raman study of a controlled functionalization of potassium intercalated graphite, revealing several new bands appearing in the D-region of the spectrum. The evolution of these bands with increasing degree of functionalization from low to moderate levels provides a basis for the deconvolution of the different components towards quantifying the extent of functionalization. By complementary DFT calculations we were able to identify the vibrational changes in the close proximity of the addend bearing lattice carbon atoms and to assign them to specific Raman modes. The experimental in situ observation of the developing functionalization along with the reoxidation of the intercalated graphite represents an important step towards an improved understanding of the chemistry of graphene.

Ataque de pie diabético. Descripción fisiopatológica, presentación clínica, tratamiento y evolución / Diabetic foot attack. Pathophysiological description, clinical presentation, treatment and outcomes

Resumen El ataque de pie diabético tiene una presentación aguda y grave que representa una amenaza para la conservación del miembro afectado e incluso para la vida del paciente. Es un término que surge por la necesidad de facilitar la identificación de aquellos pacientes que requieren intervención urgente, dándole un sentido de urgencia y gravedad, reforzando el concepto de que "tiempo es tejido". Se han identificado tres situaciones en las cuales urge este tipo de intervención: el ataque de pie diabético infectado, donde el pie se presenta con una infección grave y con rápida progresión de necrosis que requiere internación, un desbridamiento rápido de tejido desvitalizado, drenaje de colecciones y tratamiento antibiótico; el ataque de pie diabético isquémico que implica isquemia progresiva y evolutiva y requiere revascularización urgente, y la neuroartropatía de Charcot en fase aguda que demanda rápida identificación y descarga. El reconocimiento oportuno de dichas presentaciones es fundamental para iniciar un tratamiento adecuado y mejorar la evolución de los pacientes. En la presente revisión, se realiza una descripción de la fisiopatología, presentación clínica, tratamiento y evolución de los tres tipos de ataque de pie diabético.

Abstract Diabetic foot attack has an acute and severe presentation that threatens the affected limb and the patient´s life. It is a term that arises from the need to identify those patients that require urgent intervention; it conveys a sense of urgency and severity, reminding the term of "time is tissue". The classic presentation is that of a severe infected foot with rapidly progressive necrosis that requires urgent surgery to debride all necrotic tissue and purulent collections, providing an adequate antibiotic treatment. Ischemic diabetic foot attack that demands urgent revascularization and the acute Charcot neuroarthropathy for which primacy is given to diagnostic confirmation and off-loading are also considered atypical presentations of diabetic foot attack. The aim of identifying these diabetic foot presentations is to promote rapid intervention to provide adequate and effective treatment, avoiding the most feared complication which is the limb amputation. In the present review, a description of the pathophysiology, clinical presentation, treatment and evolution of the three types of diabetic foot attack is made.

Estudio de diabetes mellitus y pie diabético en la internación: datos de Argentina / Diabetes mellitus and diabetic foot in patients study: data from Argentina

Introducción: el pie diabético es una complicación que se presenta del 15 al 25% de los pacientes con diabetes mellitus (DM) a lo largo de su vida. Una vez que aparece, demanda un abordaje multidisciplinario y a menudo requiere internación. Estas internaciones suelen ser prolongadas y costosas dado que para su atención se necesitan complejos procedimientos de diagnóstico y tratamiento. En este contexto, el conocimiento de los datos acerca de la internación de pacientes con pie diabético es importante al momento de tomar decisiones de salud pública e implementar acciones para la prevención, derivación temprana, referencia y contrarreferencia de pacientes. Objetivos: el objetivo de este estudio fue determinar la prevalencia de DM y la tasa de pie diabético (PD) en pacientes internados. Materiales y métodos: se estudiaron 6.776 pacientes internados en 104 instituciones argentinas. El estudio se realizó durante un día elegido por cada institución dentro de un lapso de dos meses (septiembre y octubre de 2017). Resultados: la prevalencia de DM fue de 17,86% y la tasa de PD 14,11%. La tasa de pie diabético con lesiones Wagner 1 o mayor fue de 4,47%. El pie diabético fue el motivo de internación en el 3,16% del total de internados y al 17,85% de los diabéticos internados. Conclusiones: en nuestro conocimiento, este trabajo es el primero realizado en Argentina que abarca ese tamaño muestral y sienta precedente para nuevos trabajos de investigación en el tema

Introduction: diabetic foot is a chronic complication that occurs in 15% to 25% of diabetic patients. Once it appears, a multidisciplinary team shoud be necessary to care for that patients. Patients suffering from diabetic foot often requires treatment as inpatients. In this context, knowlege about information related to the hospitalization of diabetic foot is very important in making decisions about public health, related to prevention and treatment. Objectives: the purpose of this study was to determinate the prevalence of diabetes and the rate of diabetic foot among patients. Materials and methods: a total of 6,776 patients were studied in 104 Argentine institutions. The study was conducted during a day chosen by each institution within a period of two months (September and October 2017). Results: the prevalence of diabetes mellitus was 17.86%, while the rate of diabetic foot was 14.11%. The rate of diabetic foot classified as Wagner >=1 was 4.47%. Diabetic foot was the reason for admission in 3.16% of patients and 17.85% of diabetic patients. Conclusions: in our knowledge, this is the largest study in Argentina and lays the foundation for further investigation in this topic

Manifestation of charged and strained graphene layers in the Raman response of graphite intercalation compounds.

We present detailed multifrequency resonant Raman measurements of potassium graphite intercalation compounds (GICs). From a well-controlled and consecutive in situ intercalation and high-temperature deintercalation approach the response of each stage up to stage VI is identified. The positions of the G and 2D lines as a function of staging depend on the charge transfer from K to the graphite layers and on the lattice expansion. Ab initio calculations of the density and the electronic band structure demonstrate that most (but not all) of the transferred charge remains on the graphene sheets adjacent to the intercalant layers. This leads to an electronic decoupling of these "outer" layers from the ones sandwiched between carbon layers and consequently to a decoupling of the corresponding Raman spectra. Thus, higher stage GICs offer the possibility to measure the vibrations of single, double, and multilayer graphene under conditions of biaxial strain. This strain can additionally be correlated to the in-plane lattice constants of GICs determined by X-ray diffraction. The outcome of this study demonstrates that Raman spectroscopy is a very powerful tool to identify local internal strain in pristine and weakly charged single and few-layer graphene and their composites, yielding even absolute lattice constants.

Encuesta piloto comparativa de opinión de médicos, enfermeras y estudiantes de medicina sobre el suicidio asistido en un hospital privado del Distrito Federal / First comparative opinion survey among medical doctors, nurses and students of medicine about assisted suicide in a private hospital at the Federal District

Para conocer las opiniones del personal de salud respecto del suicidio asistido por médicos, se realizó una encuesta de opinión anónima y confidencial, tipo Likert, en un hospital privado del Distrito Federal. La población en la que se llevó acabo constó de 99 personas, de las cuales 33 son médicos, 33 son enfermeras y 33 son estudiantes de Medicina. El manejo estadístico tuvo una distribución de dos colas de ji-cuadrado, con la determinación del coeficiente de error de Pearson. El resultado principal de la encuesta muestra una diferencia significativa entre las poblaciones de estudiantes, médicos y enfermeras respecto de la aplicación del suicidio asistido por razón de calidad de vida, al que favorecen estas últimas. En las conclusiones se apunta la necesidad de impulsar el manejo de cuidados paliativos a fin de aumentar la calidad de vida de los pacientes y con ello disminuir la demanda de eutanasia. Se señala que ella es antiética, según todos los códigos deontológico mundiales, e ilegal en la mayoría de los países del mundo.