PEDOT-Carbon Nanotube Counter Electrodes and Bipyridine Cobalt (II/III) Mediators as Universally Compatible Components in Bio-Sensitized Solar Cells Using Photosystem I and Bacteriorhodopsin.

In nature, solar energy is captured by different types of light harvesting protein-pigment complexes. Two of these photoactivatable proteins are bacteriorhodopsin (bR), which utilizes a retinal moiety to function as a proton pump, and photosystem I (PSI), which uses a chlorophyll antenna to catalyze unidirectional electron transfer. Both PSI and bR are well characterized biochemically and have been integrated into solar photovoltaic (PV) devices built from sustainable materials. Both PSI and bR are some of the best performing photosensitizers in the bio-sensitized PV field, yet relatively little attention has been devoted to the development of more sustainable, biocompatible alternative counter electrodes and electrolytes for bio-sensitized solar cells. Careful selection of the electrolyte and counter electrode components is critical to designing bio-sensitized solar cells with more sustainable materials and improved device performance. This work explores the use of poly (3,4-ethylenedioxythiophene) (PEDOT) modified with multi-walled carbon nanotubes (PEDOT/CNT) as counter electrodes and aqueous-soluble bipyridine cobaltII/III complexes as direct redox mediators for both PSI and bR devices. We report a unique counter electrode and redox mediator system that can perform remarkably well for both bio-photosensitizers that have independently evolved over millions of years. The compatibility of disparate proteins with common mediators and counter electrodes may further the improvement of bio-sensitized PV design in a way that is more universally biocompatible for device outputs and longevity.

Bismuth Subcarbonate Decorated Reduced Graphene Oxide Nanocomposite for the Sensitive Stripping Voltammetry Analysis of Pb(II) and Cd(II) in Water.

In this paper, bismuth subcarbonate (BiO)2CO3-reduced graphene oxide nanocomposite incorporated in Nafion matrix ((BiO)2CO3-rGO-Nafion) was synthesized and further applied, for the first time, in the sensitive detection of Pb(II) and Cd(II) by square-wave anodic stripping voltammetry (SWASV). The as-synthesized nanocomposites were characterized by energy-dispersive spectroscopy (EDS), Raman spectroscopy, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). (BiO)2CO3 composite plays a key role in the improvement of the detection sensitivity, which can form multicomponent alloy with cadmium and lead. Additionally, the unique structure of rGO can enlarge the surface area and provide abundant active sites. Moreover, Nafion incorporation in the nanocomposite can effectively increase the adhesion and mechanical strength of the film, and further improve the preconcetration ability due to the cation-exchange capacity of its abundant sulfonate groups. As expected, the (BiO)2CO3-rGO/Nafion nanocomposite-modified glassy carbon electrode ((BiO)2CO3-rGO-Nafion/GCE) achieved low detection limits of 0.24 µg/L for Pb(II) and 0.16 µg/L for Cd(II), in the linear range of 1.0-60 µg/L, and showed some excellent performance, such as high stability, good selectivity, and sensitivity. Finally, synthetic water samples were prepared and further used to verify the practicability of the (BiO)2CO3-rGO-Nafion/GCE with satisfactory results.

Gas Biosensor Arrays Based on Single-Stranded DNA-Functionalized Single-Walled Carbon Nanotubes for the Detection of Volatile Organic Compound Biomarkers Released by Huanglongbing Disease-Infected Citrus Trees.

Volatile organic compounds (VOCs) released by plants are closely associated with plant metabolism and can serve as biomarkers for disease diagnosis. Huanglongbing (HLB), also known as citrus greening or yellow shoot disease, is a lethal threat to the multi-billion-dollar citrus industry. Early detection of HLB is vital for removal of susceptible citrus trees and containment of the disease. Gas sensors are applied to monitor the air quality or toxic gases owing to their low-cost fabrication, smooth operation, and possible miniaturization. Here, we report on the development, characterization, and application of electrical biosensor arrays based on single-walled carbon nanotubes (SWNTs) decorated with single-stranded DNA (ssDNA) for the detection of four VOCs-ethylhexanol, linalool, tetradecene, and phenylacetaldehyde-that serve as secondary biomarkers for detection of infected citrus trees during the asymptomatic stage. SWNTs were noncovalently functionalized with ssDNA using π-π interaction between the nucleotide and sidewall of SWNTs. The resulting ssDNA-SWNT hybrid structure and device properties were investigated using Raman spectroscopy, ultraviolet (UV) spectroscopy, and electrical measurements. To monitor changes in the four VOCs, gas biosensor arrays consisting of bare SWNTs before and after being decorated with different ssDNA were employed to determine the different concentrations of the four VOCs. The data was processed using principal component analysis (PCA) and neural net fitting (NNF).

Advances in mixed-matrix membranes for biorefining of biogas from anaerobic digestion.

This article provides a comprehensive review of the state-of-the-art technology of polymeric mixed-matrix membranes for CO2/CH4 separation that can be applied in medium, small, and domestic biogas systems operating at low pressures (0.2-6 kPa). Critical data from the latest publications of CO2/CH4 separation membranes were analyzed, considering the ratio of CO2/CH4 permeabilities, the CO2 selectivity, the operating pressures at which the membranes were tested, the chemistry of the polymers studied and their gas separation mechanisms. And the different nanomaterials as fillers. The intrinsic microporous polymers (PIMs) were identified as potential candidates for biomethane purification due to their high permeability and selectivity, which are compatible with operation pressures below 1 bar, and as low as 0.2 bar. This scenario contrasts with other polymers that require pressures above 1 bar for operation, with some reaching 20 bar. Furthermore, the combination of PIM with GO in MMMs was found to not influence the permeability significantly, but to contribute to the membrane stability over time, by preventing the structural collapse of the membrane caused by aging. The systematic analysis here presented is a valuable resource for defining the future technological development of CO2/CH4 separation membranes for biogas biorefining.

A bacteriorhodopsin-based biohybrid solar cell using carbon-based electrolyte and cathode components.

There is currently a high demand for energy production worldwide, mainly producing renewable and sustainable energy. Bio-sensitized solar cells (BSCs) are an excellent option in this field due to their optical and photoelectrical properties developed in recent years. One of the biosensitizers that shows promise in simplicity, stability and quantum efficiency is bacteriorhodopsin (bR), a photoactive, retinal-containing membrane protein. In the present work, we have utilized a mutant of bR, D96N, in a photoanode-sensitized TiO2 solar cell, integrating low-cost, carbon-based components, including a cathode composed of PEDOT (poly(3,4-ethylenedioxythiophene) functionalized with multi-walled carbon nanotubes (CNT) and a hydroquinone/benzoquinone (HQ/BQ) redox electrolyte. The photoanode and cathode were characterized morphologically and chemically (SEM, TEM, and Raman). The electrochemical performance of the bR-BSCs was investigated using linear sweep voltammetry (LSV), open circuit potential decay (VOC), and impedance spectroscopic analysis (EIS). The champion device yielded a current density (JSC) of 1.0 mA/cm2, VOC of -669 mV, a fill factor of ~24 %, and a power conversion efficiency (PCE) of 0.16 %. This bR device is one of the first bio-based solar cells utilizing carbon-based alternatives for the photoanode, cathode, and electrolyte. This may decrease the cost and significantly improve the device's sustainability.

Asymptomatic Diagnosis of Huanglongbing Disease Using Metalloporphyrin Functionalized Single-Walled Carbon Nanotubes Sensor Arrays.

Porphyrins, with or without metal ions (MPs), have been explored and applied in optical and electrochemical sensor fields owing to their special physicochemical properties. The presence of four nitrogen atoms at the centers of porphyrins means that porphyrins chelate most metal ions, which changes the binding ability of MPs with gas molecules via non-specific binding. In this article, we report hybrid chemiresistor sensor arrays based on single-walled carbon nanotubes (SWNTs) non-covalently functionalized with six different MPs using the solvent casting technique. The characteristics of MP-SWNTs were investigated through various optical and electrochemical methods, including UV spectroscopy, Raman, atomic force microscopy, current-voltage (I-V), and field-effect transistor (FET) measurement. The proposed sensor arrays were employed to monitor the four VOCs (tetradecene, linalool, phenylacetaldehyde, and ethylhexanol) emitted by citrus trees infected with Huanglongbing (HLB), of which the contents changed dramatically at the asymptomatic stage. The sensitivity to VOCs could change significantly, exceeding the lower limits of the SWNT-based sensors. For qualitative and quantitative analysis of the four VOCs, the data collected by the sensor arrays were processed using different regression models including partial least squares (PLS) and an artificial neural network (ANN), which further offered a diagnostic basis for Huanglongbing disease at the asymptomatic stage.

Graphene nanogap electrodes in electrical biosensing.

Graphene nanogap electrodes are reported here for the first time in an electrical biosensor for the detection of biomolecular interactions. Streptavidin-biotin was chosen as a model system for evaluating the sensor's performance. High-affinity interactions of streptavidin-gold nanoparticles (strep-AuNPs) to the biotin-functionalized nanogap localizes AuNPs, thereby bridging the gap and resulting in changes in device conductance. Biosensing performance was optimized by varying the gap size, AuNP diameter, and streptavidin coverage on AuNPs. The sensitivity and limit of detection (LOD) of streptavidin detection with the optimized parameters were determined to be 0.3 µA/nM and 0.25 pM, respectively. The proposed platform suggests high potential as a portable point-of-use biosensor for the detection of other affinity-based biomolecular interactions, such as antigen-antibody, nucleic acid, or chemo-selective interactions.

Graphene hybrids: synthesis strategies and applications in sensors and sensitized solar cells.

Graphene exhibits unique 2-D structural, chemical, and electronic properties that lead to its many potential applications. In order to expand the scope of its usage, graphene hybrids which combine the synergetic properties of graphene along with metals/metal oxides and other nanostructured materials have been synthesized and are a widely emerging field of research. This review presents an overview of the recent progress made in the field of graphene hybrid architectures with a focus on the synthesis of graphene-carbon nanotube (G-CNT), graphene-semiconductor nanomaterial (G-SNM), and graphene-metal nanomaterial (G-MNM) hybrids. It attempts to identify the bottlenecks involved and outlines future directions for development and comprehensively summarizes their applications in the field of sensing and sensitized solar cells.

Relación entre niveles de depresión y estrategias de afrontamiento en mujeres con riesgo gestacional / Relationship between levels of depression and coping strategies in women with gestational risk

Objetivo: Determinar la relación que existe entre los niveles de depresión y las estrategias de afrontamiento de mujeres con alto riesgo gestacional. Métodos: Se realizó un estudio correlacional de corte transversal, en el que participaron 70 mujeres con riesgo gestacional. Los instrumentos utilizados fueron: el inventario de estrategias de afrontamiento (CSI) en la versión española de Cano, Rodríguez y García, que cuenta con coeficientes de consistencia interna entre 0,63 y 0,89 y la Escala de depresión del centro de estudios epidemiológicos (CES-D) que cuenta con validez factorial y con una alta consistencia interna expresada en un coeficiente de Alfa de Cronbach igual a 0,87. Los datos obtenidos se organizaron con ayuda del paquete estadístico SPSS versión 13.0 y para analizar la relación entre las variables se aplicó la prueba estadística del coeficiente de correlación de Pearson. Conclusiones: La depresión presenta una relación inversa altamente significativa con las estrategias resolución de problemas y apoyo social y una relación directa altamente significativa con las estrategias autocritica, evitación de problemas y retirada social. Los sentimientos de culpa como una forma de afrontamiento son comunes durante el embarazo de riesgo. La presencia de síntomas de depresión durante el embarazo de riesgo tiene una relación directa con las estrategias de afrontamiento autocritica, evitación, retirada social y pensamiento desiderativo. Existe relación inversa entre depresión y las estrategias de afrontamiento: resolución de problemas y apoyo social. Las estrategias más utilizadas por las adolescentes que presentan embarazo de riesgo son autocritica y evitación, las mujeres en edad adulta, utilizan en mayor proporción estrategias de afrontamiento como resolución de problemas y reevaluación positiva. Las mujeres que realizan alguna actividad laboral presentan mayor uso de la estrategia búsqueda de apoyo social. No existe asociación entre los niveles de depresión presentados por las gestantes de alto riesgo y las variables sociodemográficas.

Objective: To determine the relationship between levels of depression and coping strategies in women with gestational risk. Methods: A correlational cross-sectional study was performed in which 70 women with gestational risk were involved. The instruments used were: the coping strategies inventory (CSI) in the Spanish version of Cano, Rodriguez and Garcia which count with internal consistency coefficients between 0.63 and 0.89, and the Depression scale of the epidemiological study center (CES-D), which has factorial validity and a high internal consistency expressed by Cronbach's alpha coefficient equal to 0.87. The data was organized using the statistical package SPSS 13.0 version, and the statistical test Pearson correlation coefficient was applied to analyze the relationship between the variables. Conclusions: Depression has a highly significant inverse relationship with problem solving strategies and social support, and a highly significant direct relationship with self-critical strategies, problem avoidance and social withdrawal. Feelings of guilt are common during pregnancy risk as a way of coping. The presence of depressive symptoms during pregnancy risk has a direct relationship with selfcritical coping strategies, avoidance, social withdrawal and wishful thinking. There is an inverse relationship between depression and coping strategies: problem solving and social support. The strategies most used by adolescents with high-risk pregnancy are avoidance and self-criticism, women in adulthood use to a greater extent coping strategies such as problem solving and positive reappraisal. Women doing some work activity have greater use of social support search strategy. No association between levels of depression presented by high risk pregnancies and sociodemographic variables exist.

El abuso sexual y el intento suicida asociados con el malestar depresivo y la ideación suicida de los adolescentes / Sexual abuse and suicide attempt associated with recent depressive distress and suicide ideation in adolescents

En 1998 se detectó en el Distrito Federal la conducta suicida de la población estudiantil de secundaria y bachillerato, o su equivalente, en 4.3 por ciento de los hombres y 12.1 por ciento de las mujeres. Los motivos de esta conducta pueden ser múltiples; entre ellos se encuentra el abuso sexual, que aunque ha sido poco investigado en nuestro país entre la población escolar, se ha reportado una prevalencia de 4.3 por ciento entre estudiantes de secundaria y bachillerato de ambos sexos. Este artículo pretende explorar la asociación que hay entre ambos fenómenos, y saber cómo influye en la salud mental de los estudiantes de secundaria, en lo referente al malestar depresivo y la ideación suicida. Por lo anterior se llevó a cabo un estudio en dos secundarias del Centro Histórico de la Ciudad de México. Participaron 936 alumnos de los cuales 54 por ciento eran varones y 46 por ciento mujeres, de 13.7 años en promedio. Se hizo una encuesta con el consentimiento previo de la Secretaría de Educación Pública y de autoridades escolares. Se utilizó un cuestionario autoadministrado. La participación fue voluntaria y se garantizó el anonimato y confidencialidad. No hubo rechazos. Entre los resultados destaca que 7 por ciento de las mujeres y 2 por ciento de los varones reportaron haber experimentado el abuso sexual; y 11 por ciento de las mujeres y 4 por ciento de los hombres habían intentado suicidarse. Los varones no reportaron conjuntamente estos dos problemas; mientras que de las 49 mujeres que habían intentado suicidarse, el 12 por ciento había sido también víctima del abuso sexual. La frecuencia del malestar depresivo y de la ideación suicida actuales en hombres fue de 14 por ciento y 15 por ciento, respectivamente. En mujeres fue de 18 por ciento en ambos indicadores. La presencia simultánea de estos indicadores fue de 8 por ciento en los varones y de 12 por ciento en las mujeres. La relación entre el abuso sexual y el intento suicida, con los indicadores de malestar emocional actual, fue estadísticamente significativa. De los hombres que habían intentado suicidarse, 50 por ciento presentó malestar depresivo e ideación suicida actuales; y en las mujeres que habían sido atacadas sexualmente y que habían intentado suicidarse, se presentó una alta proporción (67 por ciento) de estas problemáticas. Estos resultados comprueban la necesidad de establecer estrategias de prevención para la detección oportuna y la promoción de la salud emocional de la población escolar