Lateral size reduction of graphene oxide preserving its electronic properties and chemical functionality

Graphene oxide (GO) is widely considered as a graphene precursor when chemically reduced. Nevertheless, through the precise control of two parameters: lateral size and oxidation degree, GO can be useful in many applications as modified graphene oxide or functional reduced graphene oxide. Commonly, the decrease in GO lateral size, involves a change in the C/O ratio and therefore a modification in a large number of characteristics. Here, a simple but effective approach to synthesize GO with lateral dimensions below 100 nm and without modification of its chemical, optical and electronic features is presented. The use of a sonifier at low temperature allows to rapidly reduce the lateral size in similar to 82% while preserving the C/O ratio and consequently the chemical stability, the band gap, the electronic energy levels and the functionality. This method will allow several applications from biomedicine to energy, where reliable reduced size of GO is required

Effectiveness of bioceramics in the maintenance of pulp vitality in direct pulp covering in primary and permanent dentition: systematic review with meta-analysis

Introducción: Se han desarrollado materiales bioactivos para el recubrimiento pulpar directo con el objetivo de preservar la pulpa dentaria y mantener el diente por mayor tiempo en la cavidad oral. Objetivo: El objetivo de esta revisión fue evaluar la efectividad del uso de bioceramicos como material de recubrimiento directo pulpar para mantener la vitalidad pulpar en dientes primarios y permanentes con pulpitis reversible. Metodología: Se realizó una revisión sistemática con meta análisis. Se estudió el éxito en el tratamiento del mantenimiento de la vitalidad, el dolor postoperatorio y la decoloración. Se realizó una búsqueda Electrónica en las bases de datos: MEDLINE, EMBASE, COCHRANE, SCOPUS, LILACS, BBO. Se extrajeron los datos y se analizaron con Rev Man. Resultados: Se incluyeron ensayos clínicos aleatorizados en la cual se realizaron recubrimiento pulpar directo con silicatos tricalcicos comparado con otros materiales de recubrimiento. Comparando tres biocerámicos no se encontraron diferencias significativas en el mantenimiento de la vitalidad pulpar. En cuanto a la decoloración se observaron diferencias estadísticamente significativas a favor de Biodentine (p <0,001).  Discusión: la relevancia clínica de estos hallazgos es discutible debido a su pequeña magnitud general y al alto riesgo de sesgo de los estudios incluidos.Introduction: Bioactive materials have been developed for direct pulp capping in order to preserve the dental pulp and keep the tooth longer in the oral cavity. Objective: The objective of this review was to evaluate the effectiveness of the use of bioceramics as direct pulp capping material to maintain pulp vitality in primary and permanent teeth with reversible pulpitis. Methods: A systematic review with meta-analysis was performed. Success in treating vitality maintenance, postoperative pain, and discoloration was studied. An electronic search was carried out in the databases: MEDLINE, EMBASE, COCHRANE, SCOPUS, LILACS, BBO. Data were extracted and analyzed with Rev Man. Results: Randomized clinical trials in which direct pulp capping with tricalcium silicates was performed compared with other capping materials were included. Comparing three bioceramics, no significant differences were found in the maintenance of pulp vitality. Regarding discoloration, statistically significant differences were observed in favor of Biodentine (p <0.001). Discussion: the clinical relevance of these findings is debatable due to their small overall magnitude and the high risk of bias of the included studies

Improved charge storage performance of a layered Mo1.33C MXene/MoS2/graphene nanocomposite

The construction of nanocomposite electrodes based on 2D materials is an efficient route for property enrichment and for exploitation of constituent 2D materials. Herein, a flexible Mo1.33C i-MXene/MoS2/graphene (MOMG) composite electrode is constructed, utilizing an environment-friendly method for high-quality graphene and MoS2 synthesis. The presence of graphene and MoS2 between MXene sheets limits the commonly observed restacking, increases the interlayer spacing, and facilitates the ionic and electronic conduction. The as-prepared MOMG electrode delivers a volumetric capacitance of 1600 F cm(-3) (450 F g(-1)) at the scan rate of 2 mV s(-1) and retains 96% of the initial capacitance after 15 000 charge/discharge cycles (10 A g(-1)). The current work demonstrates that the construction of nanocomposite electrodes is a promising route towards property enhancement for energy storage applications

Alkyl-Amino Functionalized Reduced-Graphene-Oxide–heptadecan-9-amine-Based Spin-Coated Microsupercapacitors for On-Chip Low Power Electronics

With the miniaturization of microelectronics, integrated circuits can benefit from an on-chip solid-state power supply. Microsupercapacitors (MSCs), owing to their long lifetimes and complementary metal-oxide-semiconductor (CMOS) compatible fabrication, can be a potential on-chip energy storage unit. MSCs fabricated through spin coating graphene-oxide (GrO) often suffer from insufficient electrode thicknesses that lead to low energy densities. It, therefore, requires functionalizations for GrO that can improve the MSC electrode thickness and, thereby, the performance of the MSC. Thus, herein, the MSCs fabricated of alkyl-amino functionalized reduced-graphene-oxide–heptadecan-9-amine (rGO) are reported for enhanced electrode thickness, high capacitance, and lower series resistance compared with functionalized GrO-based MSCs (GO-MSCs). The functionalized rGO solves a significant issue of inadequate electrode thickness in wafer-scale MSC fabrication while achieving higher energy densities in fewer spin coatings. The rGO-MSC displays an areal capacitance of 108 μF cm−2\ua0compared with 24 μF cm−2\ua0for the GO-MSC while also demonstrating more than twice its power density in an integration compatible ionic liquid electrolyte 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfony)imide (EMIM-TFSI)

Spin-Coated Heterogenous Stacked Electrodes for Performance Enhancement in CMOS-Compatible On-Chip Microsupercapacitors

Integration of microsupercapacitors (MSCs) with on-chip sensors and actuators with nanoenergy harvesters can improve the lifetime of wireless sensor nodes in an Internet-of-Things (IoT) architecture. However, to be easy to integrate with such harvester technology, MSCs should be fabricated through a complementary-metal-oxide-semiconductor (CMOS) compatible technology, ubiquitous in electrode choice with the capability of heterogeneous stacking of electrodes for modulation in properties driven by application requirements. In this article, we address both these issues through fabrication of multielectrode modular, high energy density microsupercapacitors (MSC) containing reduced graphene oxide (GO), GO-heptadecane-9-amine (GO-HD9A), rGO-octadecylamine (rGO-ODA), and rGO-heptadecane-9-amine (rGO-HD9A) that stack through a scalable, CMOS compatible, high-wafer-yield spin-coating process. Furthermore, we compare the performance of the stack with individual electrode MSCs fabricated through the same process. The individual electrodes, in the presence of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfony)imide (EMIM-TFSI), demonstrate a capacitance of 38, 30, 36, and 105 μF/cm^2\ua0at 20 mV/s^1\ua0whereas the fabricated stack of electrodes demonstrates a high capacitance of 280 μF/cm^2 at 20 mV/s^1 while retaining and enhancing the material-dependent capacitance, charge retention, and power density

2D materials and conjugated small molecules: from synthesis to devices for energy applications

The main goal of the present work is to contribute to the area of renewable energy storage, through the precise engineering of 2D materials and conjugated materials. Thus, four different types of graphene-based materials and a conjugated small molecule were synthesized in order to successfully develop supercapacitors. In the case of graphene-based materials, it was possible to modify its main parameters such as lateral dimensions, dispersibility, and energy levels. Furthermore, a new graphene-based material (SOG), that combines the advantages of GO and graphene without their disadvantages, was synthesized. SOG shows water dispersibility, a C/O ratio 260% higher than GO, and most importantly, a very high crystallinity degree, with an ID/IG of 0.414.\ua0 The synthesized SOG exhibits an ultra-low optical band gap of 0.04 eV, which is 75 times lower compared to GO. Moreover, the electrical resistance is nine orders of magnitude smaller (1.12 KΩ/sq) compared to GO. In order to analyze the feasibility of SOG for energy storage application, a swagelok-based supercapacitor was fabricated which exhibited remarkable characteristics such as 16 474 mF g-1 of gravimetric capacitance, and good retention at 10 000 mV s-1 of scan rate. SOG characteristics make it a promising new material for applications in organic electronics. Finally, a novel perylene diimide-based (PDI) and indacenodithieno[3,2-b]thiophene (IDTT) small molecule has been successfully synthesized and used for the first time as an organic-electrode supercapacitor. This new approach circumvents complex issues regarding the synthesis and purification of polymers. Promising results of a nanocomposite made of this SM and 10% SOG demonstrate a synergistic effect of 48.75% increase in the capacitance at 10 mA g-1, in two-electrode cells for a practical demonstration in energy storage. This study may open new possibilities for fabricating supercapacitors and multifunctional devices from conjugated small molecules and graphene-based materials

Fluorinated Photovoltaic Materials for High-Performance Organic Solar Cells

Over the past decade, organic solar cells (OSCs) have achieved a dramatic boost in their power conversion efficiencies from about 6 % to over 16 %. In addition to developments in device engineering, innovative photovoltaic materials, especially fluorinated donors and acceptors, have become the dominant factor for improved device performance. This minireview highlights fluorinated photovoltaic materials that enable efficient OSCs. Impressive OSCs have been obtained by developing some important molds of fluorinated donor and acceptor systems. The molecular design strategy and the matching principle of fluorinated donors and acceptors in OSCs are discussed. Finally, a concise summary and outlook are presented for advances in fluorinated materials to realize the practical application of OSCs

Polymer Coatings Based on Nanocomposites

In particular, the development of polymeric nanocomposites has become an opportunity to meet the demands of functional materials. Polymer nanocomposites offer the possibility of new materials with a unique manifold of structure-property relationships. The formulation strategy of polymer coatings based on nanocomposites depends on the application and different approaches can be followed. In organic photovoltaics, the most important component is the active layer, which basically is a conjugated polymer nanocomposite coating. The development and design of polymer nanocomposites-enabled coatings has gained research importance as they offer the promise of incremental and disruptive improvements to products and processes. Polymer nanocomposite coatings represent properties with incredible practical applications for mechanical, optical, and electronic products. Over the last decades, the role of functional coatings has considerably changed. Polymer coating technology has evolved by the increase in scientific and technological understanding of important principles. Polymer coatings based on nanocomposites offer significant product performance and cost-saving advantages with functional features

Weak Makes It Powerful: The Role of Cognate Small Molecules as an Alloy Donor in 2D/1A Ternary Fullerene Solar Cells for Finely Tuned Hierarchical Morphology in Thick Active Layers

Herein, a novel small molecule donor is first developed, FSM6, which is a cognate molecule to BTR possessing similar molecular structure with comparable optical absorption but different crystallinity. The efficient fullerene-type ternary small molecular solar cells (SMSCs) based on an alloy donor of BTR and FSM6 in a thick film of 250 nm reveal the improved hierarchical phase separation morphology and molecular structural order of ternary active layers with improved crystallinity of the key donor component BTR. Furthermore, FSM6 as the key third component also plays a role of charge transfer accelerator in ternary SMSCs. As a result, the optimal ternary SMSCs based on BTR:FSM6:PC71BM achieve a high power conversion efficiency (PCE) up to 10.21% with the synergistically improved open-circuit voltage of 0.950 V, short-circuit current density of 13.85 mA cm(-2), and fill factor of 77.6%, in comparison with either the binary SMSCs of BTR:PC71BM (PCE = 9.37%) or FSM6:PC71BM (PCE = 8.00%). This work provides a promising methodology to optimize device morphology for high-performance ternary SMSCs by combining two cognate small molecules with similar absorption spectra but different crystallinity as an alloy donor

Highly crystalline selectively oxidized graphene for supercapacitors

Graphene oxide (GO) is usually regarded as a graphene precursor for scalable synthesis, mainly due to its aqueous processability from introducing oxygen functionalities. Nevertheless, the precise control of graphene\u27s oxidation degree to obtain a good balance between dispersion stability and crystallinity remains challenging. This study describes a simple and practical approach to synthesize a new graphene-based material called selectively oxidized graphene (SOG), which combines the advantages of graphene and GO. SOG shows water stability of −36.2 mV, a C/O ratio of 5.2, and most importantly, a very high crystallinity degree, with an ID/IG of 0.414. The synthesized SOG exhibits an ultra-low optical band gap of 0.04 eV, 75 times lower than GO. Moreover, the electrical resistance, 1.12 KΩ/sq is nine orders of magnitude smaller than GO. Additionally, it also shows promising 3-electrode capacitance with an improvement above 400 % compared to exfoliated graphene. A Swagelok-based supercapacitor was fabricated to analyze the feasibility of SOG for energy storage applications, which exhibited remarkable characteristics such as ∼ 93F g−1 capacitance and ∼ 99.8 % retention after 10,000 cycles. The characteristics of SOG ensure that this new material is promising for applications in organic electronics