Rational Design of Advanced Functional Materials for Electrochemical Devices

In recent years, there has been a fast-growing trend in developing urea (CO(NH2)2) as a substitute H2 carrier in energy conversion due to its high energy density, nontoxicity, stability, and nonflammability. Urea, a byproduct in the metabolism of proteins and a frequent contaminant in wastewater, is an abundant compound that has demonstrated favorable characteristics as a hydrogen-rich fuel source with 6.7 wt % gravimetric hydrogen content. Also, there is 2-2.5 wt % urea from mammal urine; therefore, 0.5 million ton of additional fuels will be produced per year just from human urine (240 million ton each year). Electrochemical oxidation has been recognized as an efficient strategy for urea conversion and wastewater remediation. Thus, the chemical energy harvested from urea/urine can be converted to electricity via urea oxidation reaction (UOR). Moreover, the removal of urea from water is a priority for improving drinking water quality and presents an opportunity for UOR. However, the transition of UOR from theory and laboratory experiments to real-world applications is largely limited by the conversion efficiency, catalyst cost, and feasibility of wide-spread usage. Therefore, utilization of urea using electrochemical method is a ‘two birds with one stone’ strategy which convert wastewater to electricity via anodic urea oxidation reaction (Seen in Chapter 2). Developing efficient and low-cost urea oxidation reaction (UOR) catalysts is a promising but still challenging task for environment and energy conversion technologies such as wastewater remediation and urea electrolysis. NiO nanoparticles that incorporated graphene as the NiO@Graphene composite were constructed to study the UOR process in terms of density functional theory. The single-atom model, which differed from the previous used heterojunction model (Chapter 2), was employed for the adsorption/desorption of urea and CO2 in the alkaline media. As demonstrated from the calculated results, NiO@Graphene prefers to adsorb the hydroxyl group than urea in the initial stage due to the stronger adsorption energy of the hydroxyl group. After NiOOH@Graphene was formed in the alkaline electrolyte, it presents excellent desorption energy of CO2 in the rate-determining step. Electronic density difference and the d band center diagram further confirmed that the Ni(III) species is the most favorable site for urea oxidation while facilitating charge transfer between urea and NiO@Graphene. Moreover, graphene provides a large surface for the incorporation of NiO nanoparticles, enhancing the electron transfer between NiOOH and graphene and promoting the mass transport in the alkaline electrolyte. Notably, this work provides theoretical guidance for the electrochemical urea oxidation work (As presented in Chapter 3). In addition, urea oxidation reaction (UOR) has been known as a typical energy conversion reaction but is also a viable method for renal/liver disease diagnostic detection. Here, we reported the three-dimensional nickel oxide nanoparticles decorated on the carbonized eggshell membrane (3D NiO/c-ESM) as a modified electrode toward urea detection. The electrocatalysts are characterized by XRD, SEM, and EDX to confirm its structural and morphological information. NiO/c-ESM modified electrode exhibits an outstanding performance for urea determination with a linear range from 0.05 to 2.5 mM, and limit detection of ~20 μM (3σ). This work offered a green approach for introducing 3D nanostructure through employing biowaste ESMs as templates, providing a typical example for producing new value-added nanomaterials with urea detection (Presented in Chapter 4). Generally, urea oxidation reaction happens on the anode, less attention is paid on the cathode. In fact, hydrogen evolution reaction happens on cathode during water/urea electrolysis. Therefore, in this chapter (Chapter 5), we focus our attention on the cathodic reaction, as follows: Transition metal oxides (TMOs), especially nickel oxide (NiO), are environmentally benign and cost-effective materials, and have recently emerged as potential hydrogen evolution reaction (HER) electrocatalysts for future industrial scale water splitting in alkaline environment. However, their applications in HER electrocatalysts remain challenging because of poor electronic conductivity and unsatisfactory activity. Besides, the disposal of eggshell waste is also an environmentally and economically challenging problem because of food industry. Here, we report the synthesis of NiO nanoparticles (NPs) encapsulated in the carbonization of eggshell membrane via a green and facile approach for HER application. Noteworthy to mention here that the active carbon was made from the waste, eggshell membrane (ESM), meanwhile, the eggshell was used as a micro-reactor for preparation of electrocatalyst, NiO/C nanocomposite. Then, the as-prepared NiO/C nanocomposite was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive x-ray spectroscopy (EDS). The SEM, EDS and TEM images reveal that NiO nanoparticles distributed on the carbon support, and XRD patterns confirm the presence of the nanoparticles are NiO and C hybrids. The catalytic activity and durability of NiO/C nanocomposite was examined for HER in 1 M KOH solution. It has been observed that NiO/C nanocomposite showed the better catalytic activity with the smallest Tafel slope of 77.8 mV dec−1 than single component\u27s result, NiO particles (112.6 mV dec−1) and carbonization of ESM (94.4 mV dec−1). It indicates that the HER performance of electrocatalyst can be enhanced by synergistic effect between NiO particles and carbonization of ESM, with better durability after 500 CV cycles. Furthermore, such design principle for developing interfaces between TMOs and C by a green and facile method can offer a new approach for preparing more efficient electrocatalysts (Seen in Chapter 5). Differed from other chapters, Chapter 4 focuses on the electroanalytical application of advanced nanomaterials. In this chapter, the sweep wave voltammetry (SWV) method was used for molecule detection. It is noted that we also developed several methods to detect small molecules, including differential pulse voltammetry (DPV) and chronopotentiometry (i-t). Therefore, several novel nanomaterials like gold nanoparticles and ZIF-8, two-dimensional nickel phthalocyanine-based metal-organic framework compounds were synthesized, respectively, and then used for the electroanalytical application, listed as Appendix A and B avoiding breaking the logistic of the whole manuscript

Vacuum template synthesis of multifunctional nanotubes with tailored nanostructured walls

A three-step vacuum procedure for the fabrication of vertical TiO2 and ZnO nanotubes with three dimensional walls is presented. The method combines physical vapor deposition of small-molecules, plasma enhanced chemical vapor deposition of inorganic functional thin films and layers and a postannealing process in vacuum in order to remove the organic template. As a result, an ample variety of inorganic nanotubes are made with tunable length, hole dimensions and shapes and tailored wall composition, microstructure, porosity and structure. The fabrication of multishell nanotubes combining different semiconducting oxides and metal nanoparticles is as well explored. This method provides a feasible and reproducible route for the fabrication of high density arrays of vertically alligned nanotubes on processable substrates. The emptying mechanism and microstructure of the nanotubes have been elucidated through SEM, STEM, HAADF-STEM tomography and energy dispersive X-ray spectroscopy. In this article, as a proof of concept, it is presented the straightforward integration of ZnO nanotubes as photoanode in a photovoltaic cell and as a photonic oxygen gas sensorPeer reviewe

Vacuum template synthesis of multifunctional nanotubes with tailored nanostructured walls

A three-step vacuum procedure for the fabrication of vertical TiO2 and ZnO nanotubes with three dimensional walls is presented. The method combines physical vapor deposition of small-molecules, plasma enhanced chemical vapor deposition of inorganic functional thin films and layers and a postannealing process in vacuum in order to remove the organic template. As a result, an ample variety of inorganic nanotubes are made with tunable length, hole dimensions and shapes and tailored wall composition, microstructure, porosity and structure. The fabrication of multishell nanotubes combining different semiconducting oxides and metal nanoparticles is as well explored. This method provides a feasible and reproducible route for the fabrication of high density arrays of vertically alligned nanotubes on processable substrates. The emptying mechanism and microstructure of the nanotubes have been elucidated through SEM, STEM, HAADF-STEM tomography and energy dispersive X-ray spectroscopy. In this article, as a proof of concept, it is presented the straightforward integration of ZnO nanotubes as photoanode in a photovoltaic cell and as a photonic oxygen gas sensorJunta de Andalucia TEP8067 FQM-6900 FQM 1851 P12-FQM-2265España Mineco CONSOLIDER-CSD 2008-00023 MAT2013-40852-R MAT2013-42900-P MAT2013-47192-C3-3-R RECUPERA 2020Unión Europea FP/2007-2013 312483 - ESTEEM2 291522 - 3DIMAGE REGPOT-CT-2011-285895-Al-NANOFUNC

PHOTOVOLTAIC CELLS BASED ON COPPER PHTHALOCYANINE AND CADMIUM SULFIDE HETEROJUNCTION

This work focuses on the solar cell based on the heterostructure formed between Copper Phthalocyanine (CuPc) and Cadmium Sulfide (CdS). Two different fabrication techniques were used for depositing the organic and inorganic layers of CuPc and CdS layers respectively. CuPc was deposited by electrodeposition while CdS was deposited by chemical bath deposition. Hybrid CdS/CuPc thin films were obtained from CdS films grown on Glass/ITO by chemical bath deposition followed by electrodeposition of CuPc onto these films and annealing at 250˚C after the deposition of each layer. The maximum open circuit voltage (Voc) and the short circuit current density (Jsc) obtained for this heterojunction solar cell are 0.59v and 0.7mA/cm2 respectively and these are the highest values achieved in literature till date. The materials characteristics and electrical performances of the device were analyzed. The effect of increasing the thickness of CuPc and CdS on the short circuit current density and open circuit voltage were also investigated

Phosphorescent molecular metal complexes in heterojunction solar cells

Bulk heterojunction (BHJ) solar cells have been developed intensively over the last two decades due to the cheap, flexible devices which may be obtained although their efficiency is below that of other emerging solar cell technologies such as dye-sensitized and perovskite solar cells. Molecular organometallic phosphors are noted for their triplet harvesting ability which has produced highly efficient organic light-emitting devices however triplet harvesting presents an equally appealing route to improve the efficiency of BHJ devices. The results of studies using molecular phosphors as dopants in very small loadings can yield large increases in short circuit currents and power conversion efficiency and demonstrate that improvements in solar cell performance may be obtained by this approach

Evolutionary computation for parameter extraction of organic thin film transistors using newly synthesized liquid crystalline nickel phthalocyanine

© 2019 by the authors.In this work, the topic of the detrimental contact effects in organic thin-film transistors (OTFTs) is revisited. In this case, contact effects are considered as a tool to enhance the characterization procedures of OTFTs, achieving more accurate values for the fundamental parameters of the transistor threshold voltage, carrier mobility and on-off current ratio. The contact region is also seen as a fundamental part of the device which is sensitive to physical, chemical and fabrication variables. A compact model for OTFTs, which includes the effects of the contacts, and a recent proposal of an associated evolutionary parameter extraction procedure are reviewed. Both the model and the procedure are used to assess the effect of the annealing temperature on a nickel-1,4,8,11,15,18,22,25-octakis(hexyl)phthalocyanine (NiPc6)-based OTFT. A review of the importance of phthalocyanines in organic electronics is also provided. The characterization of the contact region in NiPc6 OTFTs complements the results extracted from other physical–chemical techniques such as differential scanning calorimetry or atomic force microscopy, in which the transition from crystal to columnar mesophase imposes a limit for the optimum performance of the annealed OTFTs

Yeni sentez kobalt ftalosiyanin tabanlı organik transitör üretimi ve elektriksel karakterizasyonu

06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.Yeni sentez kobalt ftalosiyanin (CoPc) tabanlı organik alan etkili transistör (OFET) ve organik ince film transistör (OTFT) dielektrik materyal kapı olarak SiO2 ile oluşturuldu. 1-Dodecanol parçasını içeren yeni sentez kobalt ftalosiyanin 1H NMR, FT-IR, MALDI-TOF/MS, UV-Vis spektral ve termal analiz yöntemleriyle karakterize edildi. Sonrasında kompozit yarıiletken materyal ve yeni sentez CoPc tabakalı OTFT'nin elektriksel karakterizasyonu incelendi. Termal buharlaştırma yöntemiyle cihazın kaynak ve savak kısmı için Ag, kapı kısmı için de Au kaplandı. CoPc tabaka spin kaplama metoduyla hazırlandı. Yapılan ölçümler sonucunda CoPc OTFT'nin doygunluğu ( µFET ) 2,01x10-1 cm2/Vs mertebesinde olduğu görüldü. Ayrıca cihazın Ion/Ioff ve VT değerleri sırasıyla 2x102 ve -2,25 V olarak hesaplandı.Sonuç olarak yapılan çalışma bize yeni sentez CoPc'nin OTFT üzerinde kayda değer bir performansa sahip olduğunu göstermiştir. Anahtar kelimeler: OTFT, OFET, kobalt ftalosiyanin, SiO2, kompozit yarıiletken, mobiliteAn organic thin film transistor (OTFT) and organic field effect transistor (OFET), based on novel cobalt phthalocyanine (CoPc) was fabricated with SiO2 as the gate dielectric material. Novel alpha-substituted cobalt phthalocyanine bearing 1-Dodecanol moiety has been characterized by 1H NMR, FT-IR, MALDI-TOF/MS, UV-Vis spectral and thermal analysis. Subsequently, the electrical characterization of the composite semiconductor material and the new synthesized CoPc layered OTFT was investigated. Au were deposited for gate and Ag were deposited for source and drain contacts of the device by using thermal evaporation method. CoPc layer was prepared with spin coater method. The CoPc OTFT exhibited saturation at the order of µFET of 2,01x10-1 cm2/Vs. Ion/Ioff and VT of this device were calculated 2x102 and -2,25 V, respectively. The result of this study shows us that the new synthesis CoPc has a remarkable performance on OTFT. Keywords: OTFT, OFET, cobalt phthalocyanine, SiO2, composite semiconductor, mobilit

Sensing mechanism in semiconducting hybrid structures for DMMP detection

W ostatnich dwóch dekadach, w związku ze wzmożoną aktywność terrorystyczną, wzrosło zainteresowanie badaniami czujników bojowych środków trujących, w szczególności sarinu. Ze względu na wysoką toksyczność sarinu, w praktyce laboratoryjnej stosowany jest związek o podobnej budowie chemicznej - dymetylo metylofosfonian (DMMP). Większość prac dotyczących wykrywania DMMP skupia się na poszukiwaniu materiałów czułych na ten związek chemiczny i ich modyfikacji w celu uzyskania jak najlepszych parametrów czujnika. Odpowiednie zaprojektowanie urządzenia o wysokiej czułości i selektywności, a jednocześnie o niskich kosztach produkcji i eksploatacji, wymaga dogłębnej znajomości mechanizmów oddziaływania wykrywanego gazu z materiałem czułym chemicznie. W przypadku DMMP, mechanizmy te zostały zbadane dla powszechnie stosowanych w czujnikach gazów półprzewodzących tlenków metali. Wadami tych materiałów są brak selektywności i wysokie temperatury pracy. Z uwagi na to, testowane są również materiały organiczne o niskich temperaturach pracy i wyższej selektywności. Jedną z szeroko stosowanych w elektronice, w tym w czujnikach gazów, grup półprzewodników organicznych są ftalocyjaniny. Kilka prac sygnalizowało czułość ftalocyjanin względem DMMP, jednak mechanizm sensorowy nie został wyczerpująco opisany. Celem tej pracy było opracowanie metodologii badania mechanizmów sensorowych i zastosowanie jej do opisania mechanizmów wykrywania DMMP przez ftalocyjaniny oraz struktury hybrydowe oparte o ftalocyjaniny, pallad i tlenek palladu. Zastosowana metodologia składała się z części teoretycznej i eksperymentalnej. W części teoretycznej wykorzystano metody chemii kwantowej do zamodelowania adsorpcji DMMP na badanych strukturach sensorowych. Do weryfikacji wyników teoretycznych posłużyły metody eksperymentalne, takie jak: spektroskopie fotoemisyjne (XPS i UPS), spektroskopia termodesorpcji oraz pomiar odpowiedzi sensorowych metodą rezystancyjną. Badania zostały wykonane dla dwóch grup struktur: dla ftalocyjaniny wodorowej (H2Pc) z palladem (Pd) i tlenkiem palladu (PdO) oraz dla ftalocyjanin metali. W pierwszej kolejności określono mechanizm sensorowy dla struktury H2Pc/Pd/PdO, która wykazała czułość na DMMP w temperaturze pokojowej. Wyniki modelowania teoretycznego wykazały, że DMMP adsorbuje na H2Pc poprzez oddziaływania fizyczne wzmacniane przez pallad zarówno w postaci metalicznej, jak i w postaci tlenku palladu. Oddziaływanie to wywołuje znaczną zmianę momentu dipolowego układu adsorbent-adsorbat, z niewielkim przesunięciem ładunku elektrycznego. Wyniki teoretyczne zostały potwierdzone doświadczalnie w badaniu składu chemicznego powierzchni struktury H2Pc/Pd/PdO i pomiarach odpowiedzi sensorowej. Następnie, w celu optymalizacji struktury sensorowej, zanalizowano mechanizm oddziaływania DMMP z ftalocyjaninami metali, w których DMMP tworzy wiązanie poprzez tlen z centralnym atomem ftalocyjaniny. W wyniku wstępnych obliczeń teoretycznych wybrano ZnPc do szczegółowej analizy mechanizmu sensorowego. Modelowanie adsorpcji DMMP na ZnPc pokazało, że następuje transfer elektronów z cząsteczki DMMP do ftalocyjaniny, przy czym ładunek pozostaje w większości zakumulowany na wierzchniej monowarstwie ZnPc, co prowadzi do powstania silnego dipola powierzchniowego. Wyniki teoretyczne zostały potwierdzone badaniami zmian elektronowych i chemicznych w cienkiej warstwie ZnPc. Dodatkowo, dla ftalocyjanin metali potwierdzono w modelowaniu teoretycznym analogię mechanizmu sensorowego dla sarinu i DMMP

Chemical and biological sensors based on organic semiconductors

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2009.Cataloged from PDF version of thesis.Includes bibliographical references (p. 101-109).In this thesis I designed, fabricated and characterized two types of sensors: chemical sensors based on organic thin film transistors, and a miniaturized surface plasmon resonance biosensors for biotechnology and medical diagnostics applications. During completion of my research projects I designed and optimized several device architectures using numerical simulations and fundamental physical evaluation of sensing mechanism and performance. Fabricated devices were tested in custom built experimental setups in microfluidic testing chambers using automatic data measurement. Surface functionalization of device surface using self assembled monolayer techniques was employed for experiments that required specificity towards analyzed biological species.by Mihail Bora.Ph.D

Site-dependent charge transfer at the Pt(111)-ZnPc interface and the effect of iodine

The electronic structure of ZnPc, from sub-monolayers to thick films, on bare and iodated Pt(111) is studied by means of X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS) and scanning tunneling microscopy (STM). Our results suggest that at low coverage ZnPc lies almost parallel to the Pt(111) substrate, in a non-planar configuration induced by Zn-Pt attraction, leading to an inhomogeneous charge distribution within the molecule and charge transfer to the molecule. ZnPc does not form a complete monolayer on the Pt surface, due to a surface-mediated intermolecular repulsion. At higher coverage ZnPc adopts a tilted geometry, due to a reduced molecule-substrate interaction. Our photoemission results illustrate that ZnPc is practically decoupled from Pt, already from the second layer. Pre-deposition of iodine on Pt hinders the Zn-Pt attraction, leading to a non-distorted first layer ZnPc in contact with Pt(111)-I $\left(\sqrt{3}\times\sqrt{3}\right)$ or Pt(111)-I $\left(\sqrt{7}\times\sqrt{7}\right)$, and a more homogeneous charge distribution and charge transfer at the interface. On increased ZnPc thickness iodine is dissolved in the organic film where it acts as an electron acceptor dopant.Comment: 12 pages, 9 figure