Graphene/Carbon Dot Hybrid Thin Films Prepared by a Modified Langmuir-Schaefer Method

The special electronic, optical, thermal, and mechanical properties of graphene resulting from its 2D nature, as well as the ease of functionalizing it through a simple acid treatment, make graphene an ideal building block for the development of new hybrid nanostructures with well-defined dimensions and behavior. Such hybrids have great potential as active materials in applications such as gas storage, gas/liquid separation, photocatalysis, bioimaging, optoelectronics, and nanosensing. In this study, luminescent carbon dots (C-dots) were sandwiched between oxidized graphene sheets to form novel hybrid multilayer films. Our thin-film preparation approach combines self-assembly with the Langmuir-Schaefer deposition and uses graphene oxide nanosheets as template for grafting C-dots in a bidimensional array. Repeating the cycle results in a facile and low-cost layer-by-layer procedure for the formation of highly ordered hybrid multilayers, which were characterized by photoluminescence, UV-visible, X-ray photoelectron, and Raman spectroscopies, as well as X-ray diffraction and atomic force microscopy.</p

SentiBench - a benchmark comparison of state-of-the-practice sentiment analysis methods

In the last few years thousands of scientific papers have investigated sentiment analysis, several startups that measure opinions on real data have emerged and a number of innovative products related to this theme have been developed. There are multiple methods for measuring sentiments, including lexical-based and supervised machine learning methods. Despite the vast interest on the theme and wide popularity of some methods, it is unclear which one is better for identifying the polarity (i.e., positive or negative) of a message. Accordingly, there is a strong need to conduct a thorough apple-to-apple comparison of sentiment analysis methods, \textit{as they are used in practice}, across multiple datasets originated from different data sources. Such a comparison is key for understanding the potential limitations, advantages, and disadvantages of popular methods. This article aims at filling this gap by presenting a benchmark comparison of twenty-four popular sentiment analysis methods (which we call the state-of-the-practice methods). Our evaluation is based on a benchmark of eighteen labeled datasets, covering messages posted on social networks, movie and product reviews, as well as opinions and comments in news articles. Our results highlight the extent to which the prediction performance of these methods varies considerably across datasets. Aiming at boosting the development of this research area, we open the methods' codes and datasets used in this article, deploying them in a benchmark system, which provides an open API for accessing and comparing sentence-level sentiment analysis methods

Graphene nanobuds: Synthesis and selective organic derivatisation

Herein, the formation and selective organic derivatisation of graphene nanobud, an all carbon nanohybrid comprised by C60 and graphene, are presented. C60 cages are directly attached to the graphenic surface with stable covalent bonds. Importantly, prepared graphene nanobud shows remarkable dispersibility, decreased number of defects and highly aromatic character that are associated to improved electrical conductivity compared to pristine graphene. The high chemical reactivity of the curved sp2 carbon atoms of C60 led to a selective covalent attachment of organic groups onto C60 avoiding damage of the graphene aromatic system

Hydrophilic nanotube supported graphene-water dispersible carbon superstructure with excellent conductivity

In this work, it is shown that the hydrophilic functionalized multiwall carbon nanotubes (MWCNs) can stabilize a large amount of pristine graphene nanosheets in pure water without the assistance of surfactants, ionic liquids, or hydrophilic polymers. Role of stabilizer is conveyed by highly hydrophilic carbon nanotubes, functionalized by dihydroxy phenyl groups, affording a stable dispersion at concentrations as high as 15 mg mL -1 . Such multidimensional (2D/1D) graphene/MWCN hybrid is found to be dispersible also in other polar organic solvents such as ethanol, isopropanol, N , N -dimethylformamide, ethylene glycol, and their mixtures. High-resolution transmission microscopy and atomic force microscopy (AFM) including a liquid mode AFM manifest several types of interaction including trapping of multiwalled carbon nanotubes between the graphene sheets or the modifi cation of graphene edges. Molecular dynamic simulations show that formation of an assembly is kinetically controlled. Importantly, the hybrid can be deposited on the paper by drop casting or dispersed in water-soluble polymers resulting in record values of electrical conductivity (sheet resistance up to R s ≈ 25 Ω sq-1 for free hybrid material and R s ≈ 1300 Ω sq -1 for a polyvinilalcohol/hybrid composite fi lm). Thus, these novel water dispersible carbon superstructures reveal a high application potential as conductive inks for inkjet printing or as highly conductive polymers

Wetting behavior of plasma treated low-k films in dHF cleans solutions

Post-ash and post-etch cleaning of low-k structures require significant wetting of their surfaces. This work focuses on the interactions between dilute HF cleaning chemistries (dHF - 1:50 to 1:1000) on porous low-k surfaces (k = 2.3) as a function of time. Wetting of these solutions was measured by a contact angle goniometer within a high humidity environment. Because ashing low-k films can change their surface chemistry and structure, the contact angles of dHF on N2/H2 and O2 ashed porous low-k films were measured as well. Ellipsometry has shown that 1:50 HF removes an ash-damaged layer from the low-k. Based on thickness loss measurements (ellipsometry and profilometry), the composition of the dilute HF droplet changes minimally as it etches the dielectric surface. Under more concentrated dHF solutions, changes in contact angle, droplet radius, and volume indicate that the droplet spreads for an initial period and then reaches a steady state, perhaps due to the creation of an etch inclusion on the surface. The steady state volume changes show volume loss rates similar to those expected from evaporation; however, the total volume losses are less than expected from only evaporative processes. © 2014 Elsevier B.V. All rights reserved

Gd(III)-Doped Carbon Dots as a Dual Fluorescent-MRI Probe

We describe the synthesis of Gd(III)-doped carbon dots as dual fluorescence-MRI probes for biomedical applications. The derived Gd(III)-doped carbon dots show uniform particle size (3–4 nm) and gadolinium distribution and form stable dispersions in water. More importantly, they exhibit bright fluorescence, strong T1-weighted MRI contrast and low cytotoxicity