Rozprawy doktorskie na temat „MoS2 nanosheets”

Earth-abundant MoS2 is widely reported as a promising HER electrocatalyst in acidic solutions, but it exhibits extremely poor HER activities in alkaline media due to the slow water dissociation process. Here we present a combined theoretical and experimental approach to improve the sluggish HER kinetics of MoS2 electrocatalysts through engineering the water dissociation sites by doping Ni atoms into MoS2 nanosheets. The Ni sites thus introduced can effectively reduce the kinetic energy barrier of the initial water-dissociation step and facilitate the desorption of the −OH that are formed. As a result, the developed Ni-doped MoS2 nanosheets (Ni-MoS2) show an extremely low HER overpotential of ∼98 mV at 10 mA cm−2 in 1 M KOH aqueous solution, which is superior to those (>220 mV at 10 mA cm−2) of reported MoS2 electrocatalysts.

Earth-abundant MoS2 is widely reported as a promising HER electrocatalyst in acidic solutions, but it exhibits extremely poor HER activities in alkaline media due to the slow water dissociation process. Here we present a combined theoretical and experimental approach to improve the sluggish HER kinetics of MoS2 electrocatalysts through engineering the water dissociation sites by doping Ni atoms into MoS2 nanosheets. The Ni sites thus introduced can effectively reduce the kinetic energy barrier of the initial water-dissociation step and facilitate the desorption of the −OH that are formed. As a result, the developed Ni-doped MoS2 nanosheets (Ni-MoS2) show an extremely low HER overpotential of ∼98 mV at 10 mA cm−2 in 1 M KOH aqueous solution, which is superior to those (>220 mV at 10 mA cm−2) of reported MoS2 electrocatalysts.

Les technologies de séparation par membranes jouent un rôle important dans divers domaines tels que le traitement de l’eau, la séparation de produits chimiques et de gaz dans de nombreux domaines industriels ou encore l’industrie alimentaire. L’accent a récemment été mis sur les matériaux bidimensionnels(2D) pour les applications membranaires, car leur épaisseur atomique et leur espacement limité entre les couches pourraient théoriquement améliorer les performances de séparation. Les nanofeuillets eux-mêmes ou l’empilement de plusieurs feuillets peuvent former des membranes sélectives. L’empilement multicouche de monofeuillets sous forme de membrane nanolaminée crée des capillaires 2D (ou nanocanaux) capables de tamiser efficacement les espèces chimiques en fonction de leur taille. Des exemples récents ont été rapportés dans la littérature démontrant le potentiel des matériaux 2D en tant que membranes multicouches ou monocouches pour le tamisage moléculaire (222; 260; 466; 204), la séparation de gaz (219; 246; 190),la production d’énergie (467) et le dessalement de l’eau de mer (198; 194). Parmi les différentes membranes 2D nanolaminées, l’oxyde de graphène (GO) est le matériau le plus étudié, et le tamisage moléculaire au sein de sa structure est principalement dicté par la taille de ses capillaires 2D (222). Malheureusement,l’hydrophilie importante des nanofeuillets rend les membranes de GO instables en milieu aqueux, et la difficulté de contrôler la largeur des capillaires entre les nanofeuillets limite l’utilisation de ces membranes pour le traitement des eaux. D’autres matériaux 2D tels que les nanofeuillets exfoliées de dichalcogénures de métaux de transition (TMD) constituent des plateformes attrayantes pour la réalisation de membranes nanolaminées.Des travaux récents menés sur des membranes nanolaminées en disulfure de molybdène (MoS2) ont montré sa stabilité améliorée (3). Dans le cadre de cette thèse, nous avons étudié les performances d’un nouveau type de membranes nanolaminées en MoS2 pour lesquelles la chimie de surface des feuillets est précisément contrôlée (14). Afin d’évaluer le rôle de la chimie de surface,nous avons exploré l’impact de la fonctionnalisation covalente sur le tamisage moléculaire pour la purification de l’eau (plus particulièrement le dessalement et l’élimination des micropolluants) (14). Nos résultats ouvrent de nouvelles voies pour ajuster avec précision les capacités de séparation des membranes à base de matériaux 2D
Membrane separation technology plays an important role in various fields including water treatment, chemicals and gas separation for numerous industrial fields, and food processing. There has been a renewed focus on two-dimensional(2D) materials for membrane application since their atomic thicknessand confined interlayer spacing could theoretically lead to enhanced separative performances. Either the single nanosheets themselves, or the stackingof multiple sheets can form selective membranes. The multilayer assembly of single nanosheets – forming nanolaminate membranes – creates 2D capillaries(or nanochannels) that can efficiently sieve chemical species depending ontheir size.Recent examples have been reported in the literature demonstrating the potential of 2D materials as multi- or single-layer membranes for molecular sieving(222; 260; 466; 204), gas separation (219; 246; 190), energy harvesting (467)and water desalination (198; 194).Among the different building blocks of nanolaminate membranes made of two-dimensional materials (2D), graphene oxide (GO) has been studied as a candidate for molecular sieving via size-limited diffusion in the 2D capillaries (222). Unfortunately the high hydrophilicity of GO nanosheets makes GO membranes unstable in water, while the poor control of the capillary width between the nanosheets limits the water permeance of the membranes. Other 2D materials such as exfoliated nanosheets of transition metal dichalcogenides (TMDs)constitute attractive platforms for the realization of nanolaminate membranes.Recent works carried out on nanolaminate membranes made of molybdenum disulfide (MoS2) have demonstrated improved stability (3). Within this thesis we have studied the performance of a novel type of MoS2 nanolaminate membranes with well-controlled surface chemistry of the nanosheets (14). Inorder to assess the role of surface chemistry, we explored the impact of covalent functionalization on molecular sieving toward water purification (i.e. desalination and micropollutant removal) (14). Our results open novel directions to finely tune the sieving behavior of membranes based on 2D materials

The doping of rhenium into molybdenum disulfide was achieved by Aerosol Assisted Chemical Vapour Deposition (AACVD) from single source precursors. Rhenium can be studied as a model for immobilization of radioactive technetium-99 (99Tc) in MoS2. The metals Mo(IV), Re(IV), and Tc(IV) have similar ionic radii 0.65, 0.63 and 0.65 Å respectively, and their Shannon-Prewitt crystal radii 0.79, 0.77 and 0.79 Å Hence demonstrating the potential storage of nuclear waste in geologic like formations in of groundwater may be possible. The interaction between the nuclear waste forms and groundwater, which could lead to release and transport low concentrations or vapour of radionuclides to the near field, as a result, decomposition of engineered barriers. The molecular precursors [Mo(S2CNEt2)4], [Re3(μ-SiPr)3(SiPr)6], [Re(S2CC6H5)(S3CC6H5)2], and [Re2(μ-S)2(S2CNEt2)4] have been used to deposit Re-doped MoS2 thin films. Mo-doped ReS2 alloyed, polycrystalline thin films were synthesised using [Re(S2CC6H5)(S3CC6H5)2], [Mo(S2CNEt2)4] via AACVD, adding with a low concentration of Mo source for the first time . We reported as well a new way for production of ultrathin ReS2 nanosheets by coupling bottom up processing AACVD with top-down LPE. This is important in synthetic pathways for the production of rare transition dichalcogenide, also, our processing methodology is potentially scalable and thus could be a way to commercial exploitation. Characterisation of produced materials performed by pXRD, SEM, TEM, STEM, EDX, ICP and Raman spectroscopy.

La diminution de la taille des transistors actuellement utilisés en microélectronique ainsi que l’augmentation de leurs performances demeure encore au centre de toutes les attentions. Cette thèse propose d’étudier et de fabriquer des transistors à base de nanofils empilés. Cette architecture avec des grilles enrobantes est l’ultime solution pour concentrer toujours plus de courant électrique dans un encombrement minimal. Les simulations ont par ailleurs révélé le potentiel des nanofeuillets de silicium qui permettent à la fois d’optimiser l’espace occupé tout en proposant des performances supérieures aux dispositifs actuels. L’importance de l’ajout de certaines étapes de fabrication a également été soulignée. En ce sens, deux séries d’étapes de fabrication ont été proposées : la première option vise à minimiser le nombre de variations par rapport à ce qui est aujourd’hui en production tandis que la deuxième alternative offre potentiellement de meilleures performances au prix de développements plus importants. Les transistors ainsi fabriqués proposent des performances prometteuses supérieures à ce qui a pu être fabriqué dans le passé notamment grâce à l’introduction de contraintes mécaniques importantes favorables au transport du courant électrique
The future of the transistors currently used in Microelectronics is still uncertain: shrinking these devices while increasing their performances always remains a challenge. In this thesis, stacked nanowire transistors are studied, fabricated and optimized. This architecture embeds gate all around which is the ultimate solution for concentrating always more current within a smaller device. Simulations have shown that silicon nanosheets provide an optimal utilization of the space with providing increased performances over the other technologies. Crucial process steps have also been identified. Subsequently, two process flows have been suggested for the fabrication of SNWFETs. The first approach consists in minimizing the number of variations from processes already in mass production. The second alternative has potentially better performances but its development is more challenging. Finally, the fabricated transistors have shown improved performances over state-of-the-art especially due to mechanical stress induced for improving electric transport

碩士
國立臺灣科技大學
化學工程系
103
Exfoliation of bulk MoS2 via Li intercalation is an attractive route to large-scale preparation of MoS2 few-layers and it can be used to realize their unique properties in practical applications. In generally, solution-based exfoliation of layered materials results in flakes with lateral sizes of one micron or less on average. In this report, we performed the various preparations using a Li-intercalation method at room temperature to prepare MoS2 few-layers with various flake sizes according to dynamic light scattering (DLS) analysis. MoS2 few-layers with particle sizes ranging 85 to 145 nm are reported. We also characterize the few-layer MoS2 nanosheets by various microscopic and spectroscopic techniques.

This work has investigated the use of MoS2 nanosheets acting as an interlayer to effectively block polysulfide shuttling (movement from cathode to the anode) in Li-S batteries. In the first part of the work we exfoliated bulk MoS2 into a few layered MoS2 flakes, resulting in increased surface area and improved electric properties, to achieve a better interlayer performance by effectively trapping polysulfide (PS) in the cathode. This was done through solvothermal lithium intercalation followed by water sonication, creating a reaction between water and intercalated lithium to promote exfoliation. In the second part was explored the electrochemical characterization of distinct Li-S test cells (each with different interlayers), and compared to a standardized Li-S test cell. The afore mentioned interlayers were spread either on to the cathode or the separator. Furthermore, carbon black, bulk and exfoliated MoS2, were compared as active materials of the interlayers. Bulk MoS2 exfoliation into thinner flake, resulted in a size reduction up to 56 times and a decrease in the number of layers. The results of optical spectroscopy suggest effects of quantum confinement. Furthermore, with XRD, was analytically demonstrated successful intercalation and exfoliation. Then, through Raman and SEM analysis demonstrated evidence of thinner MoS2 structures. On another hand, exfoliated MoS2 was spread on a sulfur cathode creating the interlayer that successfully trapped polysulfides. This was showed through a 4 percentage points increase in sulfur utilization for the first cycle, and an improvement of sulfur loss by cycle of 0.02% retaining a good 99.4% coulombic efficiency. In addition a ΔE decreased of 45%, a result of improved battery kinetics. Nonetheless a simple carbon black DL interlayer was also made using a different solvent. However was observed a increase of sulfur utilization by 9% in the first cycle and the same degradation of sulfur per cycle as the standard battery with an impressive CE of 99.7%.

The focus of this thesis is an attempt to provide a molecular perspective of the interactions of solvent and ligand molecules with sonication assisted exfoliated MoS2 nanosheets in aqueous and non-aqueous dispersions. In this thesis both experimental measurements, notably transmission electron microscopy (TEM) and NMR spectroscopy, and molecular dynamics (MD) computer simulations have been used. This thesis consists of six chapters of which, Chapter 2 provides details of the experimental procedures and techniques as well as the classical MD simulation methodologies employed in this study. Transmission electron microscopy is critical to the present study. The in-layer structure of the nanosheets obtained was examined in greater detail from the phase corrected image reconstructed from a series of images recorded at different defocus values. Details of the exit-wave reconstruction procedure are included as an appendix to this chapter.

The unique two dimensional structure and fascinating physicochemical properties of two dimensional materials (2D) have attracted tremendous attention worldwide in disease diagnosis and nano-biomedicine. As an analogue of 2D graphene, transition metal dichalcogenides (TMDs) such as 2D MoS2/WS2 nanosheets have been exploited as representative models in numerous applications ranging from nanoelectronics to the frontiers between nanomedicine and nanotechnology. The intriguing physical and chemical properties of 2D TMDs such as confinement in dimension due to their extreme thinness, stable free standing atomic crystal nanosheets without any substrate, unparalleled surface area to volume ratio, highly biocompatible and flexibility in functionalization with different biological molecules makes them potentially favorable candidate for many biomedical applications. To get an insight into the biological and environmental fate of these engineered 2D nanosheets, it is very crucial to understand the nano-bio interactions at a prior level. Basically, the biological response to 2D nanomaterials is governed by material-specific behavior which further can be understood by the fundamental physicochemical properties of that material. Generally, three fundamental interaction modes are studied to analyze the biological impact of a given nanomaterial: a) chemical interactions, b) electronic and surface redox reactions and c) very unique physical and mechanical interactions. In general, 2DMs have shown wide range of behaviors with respect to these three modes of interactions at bio-nanosheet interface studies. Among these three modes, physical and mechanical interaction represents a unique way to study the biological response of 2D TMD nanosheets because of their high surface area to volume ratio, surface charge tuning and polarity. To exploit the full potential of 2D TMD nanosheets in biological applications, it is highly required that the given nanomaterial to be highly biocompatible, reproducible in the relevant physiological medium, flexibility in functionalization and with minimum cytotoxicity to the normal cells. In such a case and from the materials perspective, highly versatile, scalable, cost efficient and green fabrication techniques are required to obtain 2D nanosheets with the desired properties. To accomplish this aim, among various fabrication techniques reported for 2D TMDs such as chemical vapor deposition, electrochemical exfoliation, lithium intercalation, hydrothermal, sol-gel and liquid phase exfoliation, the latter one is the most versatile, scalable and cost effective technique for the production of few-layer nanosheets (1–10 stacked monolayers), with low monolayer content. Particularly in this technique, a careful optimization of exfoliation parameters such as, choice of green solvents, initial concentration of the solution, exfoliation time and controlled centrifugation for size and thickness selection of 2D nanosheets is very crucial to understand their environmental impact and behavior in biological media. To this aim, my PhD project is focused on the noticeable progress on green and scalable production of MoS2 nanosheets in water as a pure solvent, having stability up to three weeks or more by carefully optimizing critical exfoliation parameters. Such a long stability time in water, which is a non-trivial result, is crucial to test the impact of 2DMs with biological live matter in its native context, as experiments aimed at these goals may take a few days or even longer to be completed. Thus, we stress that our innovative preparation of naked MoS2 nanosheets in water solvent represents an essential step ahead for an appropriate characterization of 2DMs – live matter interactions in its natural environment. Till date, our group has investigated the biological interactions of bare MoS2 nanosheets with three different kinds of human cells, two tumoral, MCF7 (breast cancer) and U937 (leukemia), and one normal, HaCaT (epithelium), and two different kinds of Salmonella- ATCC 14028 and wild type S.typhimurium. It is worth noting that while MCF, and HaCaT cells have been already partly investigated with respect to their interactions with MoS2 nanosheets, U937-MoS2 interactions are completely unknown so far. Yet, MCF7 (Breast Cancer), Hela (Human Cervical Cancer), PC3 (Human Prostate Cancer), SMCC-7721 (Human Hepatocellular Carcinoma), B16 (Mouse Melanoma) and A549 (Human Lung Carcinoma) as cancer cell lines have been also recently tested as models by other research groups for the interactions between human cells and 2D functionalized nanomaterials of various composition, there including 2D Black Phosphorus nanosheets, 2D Boron nanosheets, 2D Antimonene quantum dots, 2D Antimonene nanosheets and Tin Sulfide nanosheets. Here, we found a very interesting and novel result from our experiments: the impact of MoS2 nanoflakes was found to be quite different in normal from cancer cell lines. While the latter cells revealed a significant cytotoxic effect based on a very large increase of cell death, the former were essentially unaffected in this respect and only showed some mechanical damage when morphologically analyzed by SEM microscopy. This cytotoxic effect was also found to be dependent on the concentration and layer number of 2D nanoflakes. In the near future, this preliminary analysis might open up new routes for significant applications of MoS2 nanosheets as targeted anti-cancer systems. This analysis was further extended to bacteria and viruses. Particularly, we have investigated the mechanical interaction of 2D MoS2 nanoflakes with two different types of Salmonella typhimurium (ATCC 14028 and wild-type) which is a very serious Gram negative facultative anaerobe causing gastroenteritis in humans and in some cases it also results in serious neurological abnormalities with very high mortality rate. SEM analysis performed after the incubation of the complex system revealed significant damage to the bacterial morphology and leakage of intra-cellular components from the bacterial structure. Both of the salmonella types when treated with 2D MoS2 nanosheets, showed that the sharp edges of the nanoflakes can cut and/or damage bacterial membrane leading to an evident bactericidal effect. Additionally, with a motive to deposit MoS2 nanosheets onto a patterned or machined substrate, particularly silicon because of its widely explored technological significance and usage in various laser processing techniques, we have first investigated the surface structuring of silicon using femtosecond laser pulses with a broad range of repetition rates (10 Hz – 200 kHz). Careful selection of various experimental conditions results in the formation of surface patterns which paves the way for numerous interesting applications. In view of this, I have introduced some preliminary results of LPE exfoliated MoS2 nanosheets deposited onto patterned silicon substrate for investigating non-linear optics of 2D nanosheets based on their thickness and given lateral size, in ongoing projects chapter at the end of this thesis. Also, enthused from the synergistic impact of 2D MoS2 nanosheets on S. typhimurium, we are currently investigating the potential interaction of the same on two other types of bacteria such as Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). In this ongoing research, we have achieved a significant time and concentration dependent damage to bacterial morphology tested at different points. We have also extended our study to analyze the mechanical interaction of water exfoliated 2D MoS2 nanosheets on a very commonly effected contagious virus, Herpes Simplex Virus (HSV-1), which has shown a good percentage of virus inhibition treated with water exfoliated MoS2 nanosheets. In fact, further investigations are under study and some of the preliminary results have been added into the ongoing projects chapter of this thesis. In order to understand the specific mechanism of action of 2D MoS2 nanosheets on the already tested tumor and normal human cells in this thesis, we have further extended our analysis in another ongoing project to go into deeper insights of 2D MoS2 nanosheets - live matter interaction using advanced Raman microscopy technique. The cell viability and the subsequent Raman microscopic analysis performed on the MoS2 nanosheets incubated with the similar human cell lines (MCF-7, U937 and HaCaT) revealed noteworthy results confirming the specific action of MoS2 nanosheets on tumor cell line (MCF-7 and U937), whereas very little or negligible effect on normal cell line (HaCaT).

碩士
國立中山大學
化學系研究所
107
In this study, we propose that mono-layered MoS2 nanosheets (M-MoS2 NSs) were proven to be impulsively adsorb on thiolated DNA molucules, due to the existence of sulfur vacancy sites on the surface of MoS2, based on that ssDNA-capped M-MoS2 NSs are customized to detect perfectly matched target DNA that is hybridized with the complementary ssDNA, MoS2 NSs with thiolated DNA molecules can be further accomplished via a one-step process under the mild buffer and salt-free conditions. In addition to, the filling of thiolated DNA molecules in sulfur vacancy sites is thermodynamically favorable. Inspired by these findings, we reason that sulfur vacancies of exfoliated MoS2 NSs could directly bind to thiol-terminated complementary oligonucleotides that are designed to bind with fluorescence resonance energy transfer (FRET)-based DNA probes. To further improvement, liberated reporter flares form hairpin-shaped structures, causing quite high FRET efficiency, these flare/ssDNA-capped M-MoS2 NSs offered comparable sensitivity, good selectivity, and high-precision to quantification of potassium (K+) ion and also Adenosine Triphosphate (ATP). In addition to, M-MoS2 NSs were used as a vector to modify the thiolated oligonucleotide (cDNA-SH) on a nanosheet by ligand conjugation, and the aptamer (D-Apt-A) partially complementary to the cDNA-SH sequence. The end group-modified fluorescent probe (FAM and TAMRA), which are the donor (D) and acceptor (A) of Förster resonance energy transfer (FRET), respectively. In the presence of the analyte, D-Apt-A would be facilitate to capture and carry out the double-strand hybridization and then detach from the surface anchored cDNA of M-MoS2 NSs. The as-prepared flare/ssDNA-capped M-MoS2 NSs and G4 flare/ssDNA- and also Apt flare/ssDNA were shown to have practical applications in the quantitative determination of K+ in human plasma and ATP in erythrocytes as well as ratio metric fluorescent imaging of K+- and ATP-related reactions and TK1 mRNA in living cells along with real samples.

博士
國立交通大學
材料科學與工程學系所
102
The purpose of this work is to find out new approaches for one-pot synthesis of graphite oxide and graphene by plasma electrochemical exfoliation of graphite in a basic electrolyte solution in a short-reaction time with regards of environmental friendliness, energy/time saving, and low cost. First of all, we adopted a highly efficient cathodic plasma (CP) process in which the vapor plasma envelope calorific effect provides instant oxidation and expansion of graphite for producing plasma-expanded graphite oxides (PEGOs) from recycled graphite electrodes (GEs) or high purity graphite (HG), within a reaction time of 10 min without the need for strong oxidants or concentrated acids. X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy confirmed the dramatic structural change from GEs or HG to graphite oxides after the CP process. Furthermore, scanning electron microscopy and transmission electron microscopy revealed that the graphite oxide possessed a spheroidal morphology, with dimensions of 1–3 μm, as a result of melting and subsequent quenching during the plasma electrolysis process. We obtained a stable, homogeneous dispersion of PEGOs in N-methyl-2-pyrrolidone after sonication and filtering of the centrifuged PEGOs. We used these spheroidal graphite oxide particles as effective adsorbents for the removal of pollutants (e.g., Methylene Blue) from aqueous solutions. These PEGOs also served as good precursors for the preparation of graphite nanopletets. iv Sequently, we have demonstrated a new and highly efficient plasma-assisted electrochemical exfoliation method, involving a plasma-generated graphite cathode and a graphite anode, for the production of graphene sheets from electrodes in a basic electrolyte solution in a short reaction time. The AFM images revealed a lateral dimension of approximately 0.5–2.5 μm and a thickness of approximately 2.5 nm, corresponding to approximately seven layers of graphene, based on an interlayer spacing of 0.34 nm. Additively, the influence of electrolytic concentration on morphological and structural properties of plasmaelectrochemically exfoliated graphene is investigated and presented. Finally, we developed an efficient solution-based method for the production of few-layer MoS2 nanosheets through exfoliation of bulk MoS2 compounds that were subject to quenching in liquid N2 and subsequent ultrasonication. AFM images of individual nanosheets revealed that the thickness varied from 1.5 to 3.5 nm and the lateral dimensions from 0.5 to 3.5 μm.

No
Here we report a hierarchical composite structure composed of few-layers molybdenum disulfide nanosheets supported by vertical graphene on conductive carbon cloth (MDNS/VG/CC) for high-performance electrochemical hydrogen evolution reaction (HER). In the fabrication, 3D vertical graphene is first prepared on carbon cloth by a micro-wave plasma enhanced chemical vapor deposition (MPCVD) and then few-layers MoS2 nanosheets are in-situ synthesized on the surface of the vertical graphene through a simple hydrothermal reaction. This integrated catalyst exhibits an excellent HER electrocatalytic activity including an onset potential of 50 mV, an overpotential at 10 mA cm(-2) (eta(10)) of 78 mV, a Tafel slop of 53 mV dec(-1), and an excellent cycling stability in acid solution. The excellent catalytic performance can be ascribed to the abundant active edges provided by the vertical MoS2 nanosheets, as well as the effective electron transport route provided by the graphene arrays on the conductive substrate. Moreover, the vertical graphene offers robust anchor sites for MoS2 nanosheets and appropriate intervals for electrolyte infiltration. This not only benefits hydrogen convection and release but also avoids the damaging or restacking of catalyst in electrochemical processes.
This work was financially supported by the National Natural Science Foundation of China (Grant nos. 61176007, 51372213, and 51402343).

碩士
國立臺北科技大學
製造科技研究所
107
In this study, a horizontal furnace tube was used to synthesis vertically grown MoS2 nanosheets on SiO2 substrate by chemical vapor deposition. In the first part, the samples were synthesized by changing the ratios of different MoO3 powder to sulfur powder with the same total amount in 1 g and denoted as 1:4, 1:8, 1:16, 1:18, 1:20, 1:24 and 1:32, respectively. It was found that the MoS2 was been synthesized with smaller proportion (1:16 ~ 1:32) accompanied with minority of bulk-like MoO3 and with larger proportion (1:4 and 1:8) accompanied with majority of normal MoO2 during the growth process, respectively. These three parameters of 1:16, 1:18 and 1:20 have less bulk-like MoO2 and the highest structural height, so it is the optimal parameter from 1:16 to 1:20. Furthermore, when the ratio of MoO3 to S was increased to 1:32, the phase and the height of MoS2 nanosheets are highly reduced. In addition, after optimizing these three proportion of MoO3 to S, the total amounts of powder have been tuned from 1 to 2 g. The results show that the diffraction peak and height of MoS2 nanosheet were increased with increasing the total amount of powder. However, when the total amount up to 2 g, the bulk-like MoO2 will be observed in the sample with every proportional parameter. Therefore, the total amount of 1.7 g was the optimal parameter due to the highest nanosheet structure comparing to the others. The crystal structure and surface morphology of the samples which in ratio of 1:16, 1:18, and 1:20 with total amount of 1.7 g were demonstrated by XRD, Raman and SEM, respectively. Finally, ontact angle (CA) measurement, UV-VIS spectra and photodetector systems were employed to identify the surface wettability, water purification and photodetector capabilities, respectively.

Infectious diseases caused by pathogenic bacteria are creating a global health problem. In the recent report of World Health Organization (WHO), it has been mentioned that around 7 lacks people are dying each year worldwide due to drug resistant microbials. After discovery of the lifesaving “wonder drug” molecule penicillin, it was extensively used for the treatment of bacterial infection diseases. However, the excessive use of antibiotics leads to the development of antimicrobial resistance in the pathogenic bacterial strains to overcome the bactericidal effect of antibiotics. The drug-resistance bacteria follow multiple pathways to show resistance towards the existing antimicrobial agents and eventually make them abortive. The prevalence of these drug resistant bacterial strains poses a serious threat to the present medical system. Therefore, there is an urgency to develop advanced antimicrobial agents which can restrict the spread of pathogenic bacteria to eradicate infectious diseases. In this context, the current advancement in the field of nanotechnology would help us to develop nanomaterial-based antimicrobial agents which could be one of the possible alternatives of conventionally used antibiotics. There are numerous reports, which established that nanomaterials such as graphene oxide, carbon nanotube, noble metal nanoparticles, metal oxides like ZnO2, MnO2 etc. have possessed antibacterial activity. In particular, the use of nanosized molybdenum disulfide (MoS2), a transition metal dichalcogenide showed a great potential to utilize for the development of potent antibacterial agents owing to its unique chemical and photophysical properties. Two-dimensional MoS2 nanosheets provide a large surface to volume ratio for the effective interaction with the bacterial cell membrane. For better biological interactions of MoS2 nanomaterials, its surface modification can be easily achieved through functionalization using thiol ligand molecule. Functionalization also enhances its aqueous dispersibility in manyfold. In this thesis work, I have utilized MoS2 nanomaterials and their nanocomposites to develop nanomaterial-based effective antimicrobial agents for the pathogenic bacterial strains using multiple strategies. To extend my work towards the development of nanomaterial-based antibacterial agents, I have explored antibacterial activity of the supramolecularly self-assembled nanosized cage molecule to eradicate drug-resistant bacteria. Apart from antibacterial activity, I have also expanded the scope of applicability of our newly developed nanomaterials in the direction of bio-analyte detection and environmental remediation such as degradation of organic pollutant and detoxification of the chemical warfare agent.

碩士
國立高雄應用科技大學
化學工程與材料工程系博碩士班
104
In this study, molybdenum diselenide (MoSe2) with nano-layered structure was synthesized by a hydrothermal method. The process parameters such as reaction temperature and annealing temperature were investigated for their effects on the crystallinity, morphology of the products, and their related electrical characteristics. X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), high magnification transmission electron microscope (HR-TEM), and Raman spectroscopy (Raman) were used to analyze its crystallinity and morphology of MoSe2. The electrical characteristics was done by cyclic voltammetry and charge/discharge test. It was found that samples only being reacted in an autoclave of three different temperature, i.e., 180, 200 or 220 ℃, without further annealing exhibited amorphous structures. After further annealing, MoSe2 exhibited crystalline structure. MoSe2 annealing 400~700 ℃, are nano-particles by FE-SEM. A flower like morphology was noted in the samples of being annealed at 400 ℃. A layered structure of MoSe2 was observed by HR-TEM and proved in Raman spectroscopy. Electrochemical tests found MoSe2 exhibit pseudo-capacitance reaction. The capacitance value of 206 F/g was obtained from the charging and discharging experiments. The data proved that MoSe2 electrodes have good electrochemical characteristics.