Aim and scope. allowd ) and examples of awkward language (e.g. [in Polish] This property favours the use

Transcription

1 Professor Urszula NARKIEWICZ, Ph.D., D.Sc., Eng. Szczecin, West Pomeranian University of Technology, Szczecin Institute of Chemical and Environment Engineering Pulaskiego Szczecin Review Report on PhD Thesis of Marcin Wysokowski, M.Sc., Eng. entitled Development of Novel Inorganic-Organic Chitin-Based Materials Obtained Under Extreme Biomimetic Conditions prepared base on invitation letter from the Dean of the Faculty of Chemical Technology of Poznan University of Technology Associate Professor Krzysztof Alejski, Ph.D., D.Sc., Eng. (438/ , ) Supervisor: Prof. Teofil Jesionowski, Ph.D., D.Sc., Eng. Poznan University of Technology (Poland) Co-supervisor: Prof. dr. rer. nat. habil. Hermann Ehrlich Technische Universitaet Bergakademie Freiberg (Germany) Choice of topic Inorganic organic hybrid materials are among the most interesting and promising types of nanomaterials, and one of the most important challenges in nanotechnology is to obtain nanomaterials with a hierarchical architecture, built from nano-bricks and designed based on systems found in nature (biomimetics). In the course of millions of years of evolution, nature has produced functional materials with unrivalled parameters that we would like to be able to imitate for example, to produce fibres with the strength of spider s thread, construction materials with the hardness of certain animal shells, and coatings as perfectly unwettable as the lotus leaf. It is generally considered that the processes taking place in nature occur in moderate conditions (atmospheric pressure, ambient temperature, neutral ph), often in the presence of biocatalysts, namely enzymes. Nonetheless, examples are known of processes taking place in nature under extreme conditions, such as Arctic or hydrothermal. One example of a material formed many centuries ago in extreme conditions is amber. However, the concept of extreme biomimetics, as a technology for obtaining innovative bio-inspired materials in 1

2 extreme conditions, was introduced only recently (2010), and its originator, Professor Hermann Ehrlich, is one of the two supervisors of Marcin Wysokowski s work. With regard to the facts outlined above, I am of the opinion that the topic of Marcin Wysokowski s doctoral thesis, titled Development of New Inorganic Organic Chitin-based Materials Obtained in Conditions of Extreme Biomimetic Synthesis, is highly innovative and ideally aligned with the latest trends in contemporary materials science. Aim and scope The aim of the work was to obtain and analyse a new type of inorganic organic hybrid material based on chitin. The author decided to do this using a hydrothermal method, producing hybrid nanomaterials using a chitin-based scaffolding obtained directly from the skeletons of marine sponges and cuttlefish. Because the chitin matrices obtained are stable up to 280 C, they can be used in hydrothermal conditions to obtain hybrid nanomaterials in combination with inorganic compounds. In this way the author produced the following composites: chitin SiO2, chitin ZrO2, chitin ZnO, chitin Fe2O3 and chitin GeO2. The resulting materials were analysed using a whole spectrum of modern experimental techniques, including X-ray diffraction, Fourier transform infrared spectroscopy, high-resolution transmission and scanning electron microscopy, thermogravimetric analysis, Raman spectroscopy, X-ray photoelectron spectroscopy, selected area electron diffraction, and near-edge X-ray absorption fine structure (NEXAFS). The work also included investigation of the electrochemical, photoluminescent and antibacterial properties of individual products. Presentation The reviewed thesis of Marcin Wysokowski, M.Sc., Eng. consists of 172 pages, and refers to 364 cited works. It contains 47 figures and photographs, which are of very high quality. The thesis is written in English, and it has been very diligently edited. At the end is a summary in Polish, as well as summaries of individual chapters. This summary is editorially weaker than other parts of the thesis it contains misprints (such as devpelopment, novelity, allowd ) and examples of awkward language (e.g. [in Polish] This property favours the use of selected chitin skeletons as structural organic matrices for nucleation and growth in a wide range of hydrothermal reactions. ) What does the author mean by a wide range of reactions? Different compounds, different temperatures? Would it not have been simpler to write It is therefore possible to use chitin skeletons as organic matrices for the nucleation and growth of many inorganic crystals in hydrothermal conditions? 2

3 Could the author explain what he means by The interdisciplinary nature of the work consists in the application of a nonlinear approach to problems of biomimetics? The work does not include any mathematical modelling (hence where does the nonlinear approach come from?), and the interdisciplinary nature of the work results rather from the combining of elements of knowledge from the fields of chemistry, physics, biology and materials science. Content In the section containing an analysis of the literature, following a general introduction familiarising the reader with the scope of the work, the author provides a review of the literature covering problems of biomimetics, with particular emphasis on biomimetics in extreme conditions. A subsequent subsection concerns literature relating to chitin as an excellent structural matrix for producing the type of materials studied in the work. The final subsection in this part concerns the literature on hydrothermal synthesis. The entire literature review section is diligently compiled and may serve as a compendium of knowledge for researchers wishing to undertake work in the field of extreme biomimetics. In Chapter 3 the author presents his research goals. The main aim of the work is to use chitin scaffoldings obtained from the skeletons of marine sponges and cuttlefish to produce new inorganic organic materials in hydrothermal conditions. This goal was achieved using the materials and research methods described subsequently in Chapter 4. The first stage in the synthesis of inorganic organic materials was the preparation of the matrix, namely the obtaining of chitin silica biomaterials by way of hydrothermal silicification of chitin matrices isolated from marine sponges. The process was carried out in the presence of a mixture of ethanol, ammonia solution and a surfactant (TEOS). The chitin silica scaffoldings were subsequently used to obtain composites with the oxides of several metals zirconium, zinc, iron and germanium. All of these composites were obtained in hydrothermal conditions, although each was obtained using a different reactor and under different conditions this does not present any difficulty, as they were not intended to be the subject of comparison. It was found that silica binds to the OH, C+O and NH groups of chitin via hydrogen bonds. In the chitin ZrO2 composite, the nanoparticles of zirconium oxide are approximately 100 nm in size, and the average size of the crystallites of monoclinic ZrO2 is 4 8 nm. In this case also it was found that zirconia interacts with silica via hydrogen bonds. An attempt was made to use the resulting composite to remove heavy metals from water, and promising results were obtained: 1 g of composite is capable of 3

4 adsorbing 20 mg of cadmium (2.5 times more than in the case of pure chitin). It would appear, however, that in view of the properties of zirconium oxide (luminescence, chemical resistance, biocompatibility), the chitin zirconia composite may well find many other interesting applications, for instance in biomedicine. Similar potential applications can be expected for the chitin ZnO composite, which the author tested for its bactericidal properties. It might be used, for example, in wound dressing materials to remove Grampositive bacteria. The average size of hematite crystallites in the chitin Fe2O3 composite was estimated at approximately 57 nm. Hematite was found to interact with the NH and C=O groups of chitin. The author investigated the possibility of using these composites as fillers of activated carbon in supercapacitors the results obtained were positive, and even showed an increase in capacitance over successive cycles. Samples of the produced chitin GeO2 composite were found to contain large ( nm) crystallites of germanium oxide, but also nanocrystallites measuring around 10 nm. This composite exhibits interesting luminescent properties. Its intensity of autofluorescence is stronger than that of pure chitin or of pure germanium oxide also obtained in hydrothermal conditions. This is explained by an increase in defects, caused by the incorporation of nanofibres of the biopolymer into the GeO2 crystalline framework. This phenomenon may form a basis for successful applications in medicine, in sensors and in optoelectronics. Overall assessment The doctoral thesis written by Marcin Wysokowski contains very interesting experimental results, described in a logical and ordered manner. The candidate was required to master an entirely new, challenging and interdisciplinary field of knowledge extreme biomimetics and completed that task excellently. The literature studies contained in the thesis are exceptionally diligent, and the number of citations to published works is impressive. The author has fully attained the goal of the work, using chitin matrices obtained from the skeletons of marine organisms to produce new inorganic organic materials in hydrothermal conditions, these being the composites chitin SiO2, chitin ZrO2, chitin ZnO, chitin Fe2O3 and chitin GeO2. Praise should be given not only to the precise analysis of the composites obtained, but also to the proposals of potential applications for them, and the testing of these in laboratory conditions. 4

5 In summary, since the reviewed doctoral thesis of Marcin Wysokowski, M.Sc., Eng. in my opinion fulfils the requirements of the Act on academic and artistic degrees and titles, I propose to the Council of the Chemical Technology Faculty of Poznan University of Technology that it be admitted to the further stages of the doctoral process. This thesis is ready to be defended orally, in front of respective committee. Moreover, in view of the high quality of the thesis itself and the impressive list of publications by Marcin Wysokowski (24, including 22 in Thomson Reuters JCR list (total IF=67.9), as well as three patents and 24 conference papers), I would like to propose to the Council of the Chemical Technology Faculty of Poznan University of Technology that a distinction be awarded for this thesis. 5