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[Paper: One material, multiple functions: graphene/Ni(OH)2 thin films applied in batteries, electrochromism and sensors. Eduardo G. C. Neiva, Marcela M. Oliveira, Márcio F. Bergamini, Luiz H. Marcolino Jr & Aldo J. G. Zarbin. Scientific Reports 6, 33806 (2016). doi:10.1038/srep33806. Link para o artigo: http://www.nature.com/articles/srep33806]
A lot of science and some serendipity to discover the recipe for a multifunctional nanocomposite.
A recently published paper in the journal Scientific Reports, from the Nature group, reports a study carried out in universities of the state of Paraná (Brazil) on a material based on nickel hydroxide Ni(OH)2 – a composite of great technological interest [See box]. The group of authors developed an innovative method to fabricate a material based on nickel hydroxide graphene and nanoparticles, prepared thin films with this material and demonstrated the efficiency of these films when used as rechargeable battery electrodes, glycerol sensors and electrochromic materials.
The work was carried out within the doctoral research of Eduardo Guilherme Cividini Neiva, under the guidance of Professor Aldo José Gorgatti Zarbin, in the Chemistry Post-Graduation Program of the Federal University of Paraná (UFPR). Neiva began his research on nickel nanoparticles during his undergraduate years, guided by Professor Zarbin. In the master’s program, still with Zarbin, he developed a preparation route of nickel metal nanoparticles for electrochemical applications. After completing the master’s program, Neiva and Zarbin set out to continue the research in Neiva’s doctorate, including graphene in the preparation of nickel metal based nanoparticles to obtain nickel and graphene nanocomposites with different properties. “Most of my scientific interests focus on the preparation of materials with carbon nanostructures, such as nanotubes and graphene,” states Professor Zarbin, who is the corresponding author of the article in Scientific Reports.
They were surprised by the first laboratory results. In the presence of graphene oxide (as a precursor of graphene in the preparation of the material), the process took a different course. At that time, Neiva and Zarbin saw the potential of these particularities: if well understood, they could be controlled and used to prepare nanocomposites, not only of nickel metal, but also of nickel hydroxide, which would open up new application possibilities. “There is a phrase by Louis Pasteur I like very much, which applies perfectly in this case: “Chance favors the prepared mind,” declares Zarbin.
Based on this, student and advisor created a simple and direct process for the fabrication of graphene and nickel hydroxide nanocomposites. In this innovative process, both components are synthesized together in a one-step reaction. Using this technique, Neiva manufactured the nanocomposites. Pure nickel hydroxide samples were also produced in order to compare them with the nanocomposites.
The samples were studied through a series of techniques: X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), thermogravimetry, field emission scanning electron microscope (FEG-MEV), and also by means of transmission electron microscopy (TEM) images carried out by Professor Marcela Mohallem Oliveira, from the Federal Technological University of Paraná (UTFPR). The comparison between the two materials was favorable to the nanocomposite. “Graphene played a key role in the stabilization of particles at the nanometer scale, increasing the chemical and electrochemical stability of the nanoparticles, and increasing the conductivity of the material, which is fundamental for an improvement in the desired applications,” acknowledges Aldo Zarbin.
The next stage consisted of
processing the nanocomposites and the nanoparticles of pure nickel hydroxide to obtain thin films, a format that allows using them in the desired applications. “The deposition of materials in the form of films, covering different surfaces, is a great technological challenge, even greater when dealing with multicomponent materials and insoluble, infusible and intractable materials (all characteristics of the material reported in this article)”, explains Zarbin.
To overcome this challenge, Neiva used a processing route, known as liquid/liquid interfacial method, developed in 2010 by the research group led by Zarbin, the Materials Chemistry Group of UFPR. This route, besides simple and cheap, explains Professor Zarbin, allows depositing complex materials in the form of homogeneous and transparent films on various types of materials, including plastics. “The route is based on the high energy at the interface of two immiscible liquids (e.g., water and oil), where the material is initially stabilized to minimize this energy, allowing its subsequent transfer to substrates of interest,” he explained.
With the nanocomposites, Neiva obtained thin transparent films of about 100 to 500 nm in thickness, with nanoparticles of about 5 nm in diameter, distributed homogeneously on the graphene sheets. The pure nickel hydroxide, however, generated films formed by porous spherical nanoparticles of 30 to 80 nm in diameter, distributed heterogeneously, forming agglomerates in some regions.
In the final phase of the work, the films deposited on glass and indium tin oxide were tested in three applications, in which the nanocomposite performed better than pure nickel hydroxide. As a material for rechargeable alkaline battery electrodes, the nanocomposite exhibited high energy and high power – two positive points that are not easily found in the same material. The nanocomposite also showed good performance as an electrochemical sensor. In fact, experiments designed by Professors Márcio Bergamini and Luiz Marcolino Jr, also from UFPR, showed that the nanocomposite is a sensitive sensor of glycerol (a compound known commercially as glycerin and used in several industries). Finally, the nanocomposite acted as an efficient electrochromic material. With these characteristics, the films of the UFPR group have a chance to leave the laboratory and be part of innovative products. “This depends on partners who are interested in scaling the method and testing it on real devices,” says Zarbin.
For now, in addition to scientific articles such as the one published in the journal Scientific Reports, the work generated several patents, both on the deposition method of thin films and on their applications in gas sensors, transparent electrodes, photovoltaic devices and catalysts. “And we have now developed a flexible battery, which was only possible thanks to the film deposition technique we developed,”, adds Professor Zarbin.
The work, which was developed within the macro projects “INCT of carbon nanomaterials” and “Nucleus of Excellence in Nanochemistry and Nanomaterials”, received funding from the federal agencies Capes and CNPq, and the Araucária Foundation, an agency for scientific and technological development of the state of Paraná.
With a degree in Industrial Pharmacy at the Fluminense Federal University (UFF) and pharmacist at a multinational laboratory, André Luiz Azevedo Maia plunged in the field of Materials through his Masters degree in Chemistry, seeking to lower costs and overcome the limitations of techniques used in drug analysis. “During my career I acquired knowledge in analytical techniques that require higher spending both in the acquisition and in maintenance and operation, e.g., CLAE, GC, AA – flame and graphite furnace,” said the winner of the prize. “That motivated me to start the development of analytical techniques in Electrochemistry” he added.
André´s master thesis, supervised by Professor Felipe Silva Semaan and funded by the Rio de Janeiro State Research Foundation (FAPERJ), the Brazilian Federal Council for Scientific and Technological Development (CNPq) and UFF, was conducted between 2012 and 2014 in the Electrochemistry and Electroanalytical Group at the Institute of Chemistry, UFF, within the line of research in composite materials initiated in the group in 2009.”The use of composite materials aimed to further minimize costs for research (because there would be no need to purchase electrodes for commercial work) and opened up the possibility of developing chemical modifications and adjusting models for specific applications,” said André.
André and the research team then developed graphite and epoxy composites in various compositions, which were characterized by thermal gravimetric analysis (TGA-DTA), atomic force microscopy (AFM), X-ray diffraction (XDR) and cyclic voltammetry. One of these compositions, with 64.4% graphite, showed the best results regarding thermal and chemical stability, mechanical and electrical properties and electrochemical performance. The composite was used as an electrode in an electrochemical cell.
“In this work, the scientific contribution to society is the availability of a material with added value, with a cost about 300 times smaller than the commercial one (the glassy carbon electrode), and able to perform tasks with equivalent quality,” says André, who affirms to be attracted by the scientific activity because it offers the possibility of using tools he acquired at the university to solve problems for society.
The work presented at Symposium P on composites and advanced carbon nanostructures, deserved the Bernhard Gross Award for best poster of the XIII SBPMat Meeting, in addition to the best Poster of Symposium P. Partial results of the same research had already been distinguished in last year´s SBPMat meeting, where André received the Bernhard Gross Award for best work of the symposium on science, engineering and commercialization of industrial, electronic and biomedical devices.
André´s master degree was concluded with this highlight granted by SBPMat, but the work goes on into the group. The researchers are preparing a patent. And the results of André´s study are beeing a basis for the development of composite electrodes modified with metal films, cellulose acetate films and modified chitosan to encapsulate nanoparticles, among other studies.
“The award in this international congress rewards the effort and dedication of everyone involved and leads to further discussion, indicating the feasibility of obtaining the products targeted by the group,” said André.
See the award-winning poster file: