LEE- Nano Bilim ve Nano Mühendislik-Yüksek Lisans
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ÖgePreparation and characterization of carbon quantum dot- based composite thin films(Graduate School, 2025-06-16)Carbon quantum dots (CQDs) are zero-dimensional, carbon-based nanoparticles with fluorescence in the 2–10 nm range, offering advantages such as facile synthesis, surface functionalization, water solubility, biocompatibility, low toxicity, and simple preparation methods. Common synthesis techniques include hydrothermal, solvothermal, and microwave-assisted methods; CQDs produced via hydrothermal treatment of precursor materials exhibit quantum yields of 60–80 %. CQDs find applications across a wide spectrum, including biomedical imaging, biosensors, drug- delivery systems, photoelectrocatalysis, optoelectronics, and energy storage. In particular, their low toxicity in both in vivo and in vitro biocompatibility assays makes them suitable as fluorescent markers for diverse biomedical functions, from cancer imaging to tracking administered drug particles. Their photoluminescence emissions can be tuned to produce strong blue light around 450 nm under 350 nm excitation, enabling high-contrast cellular imaging. With quantum yields reaching up to 80 %, CQDs are versatile nanomaterials whose electronic and optical properties can be tailored for specific applications through surface modifications. Characterized by UV–Vis spectroscopy, CQDs emit intense blue light near 450 nm when excited at 350 nm. These features render them promising for smart packaging, anti-counterfeiting labels, and biosensor applications. In biosensors, CQDs leverage their surface functional groups to selectively detect analytes such as metal ions, pH changes, and glucose. The presence of metal cations, anions, or biomolecules induces measurable shifts in their photoluminescence spectra, enabling both environmental pollutant monitoring in water and visualization of ionic balance in cellular environments. In energy technologies, CQDs enhance photoelectric conversion and energy storage in devices ranging from solar cells to supercapacitors. By adjusting their size and surface chemistry to tune bandgaps, CQDs serve as photosensitizers in dye-sensitized solar cells, significantly boosting power conversion efficiencies in both organic and perovskite systems. In optoelectronic devices, CQD-based light-emitting diodes (LEDs) and fluorescent dyes offer compact, low-cost lighting solutions for flexible display technologies and smart packaging. For example, CQD-LEDs have been developed to deliver tunable colors and broad emission spectra. When integrated into polymer matrices, CQDs block approximately 70–90 % of UV radiation, thereby providing UV protection and extending the lifespan of packaging and coating materials. Additionally, their bright blue fluorescence under UV illumination generates directly readable signals for anti-counterfeiting tags and smart- packaging sensors. In food packaging and security labelling, CQD-functionalized surfaces emit vibrant blue fluorescence under UV light, serving both as shelf-life indicators and as easily readable anti-counterfeiting markers. In the field of food packaging, CQDs play critical roles in active packaging strategies through UV protection, strong moisture-barrier properties, antibacterial activity, and antioxidant functions. Antimicrobial agents immobilized on CQD surfaces inhibit microbial growth within packages, thereby extending product shelf life. These functionalities are widely researched in nanocomposite film technologies to ensure consumer safety and product quality. Facing the environmental pollution and microplastic threats posed by petroleum-based plastics, biodegradable polymers have become the focus of sustainable packaging solutions. Alongside PLA, PHA, PBS, and PBAT, starch-based materials offer cost- effectiveness and biodegradability. Key parameters for biodegradable polymers include mechanical strength, oxygen and water-vapor barrier performance, thermal stability, and cost balance. Active and smart packaging increasingly incorporates antimicrobial or antioxidant additives and sensor functionalities to manage food safety and shelf life. Starch, an abundant and low-cost polysaccharide, is prominent in biodegradable film production. However, pure starch films suffer from brittleness and high water-vapor permeability, which limit their use in food-packaging applications. To overcome these weaknesses, composite films have been developed by incorporating plasticizers such as glycerol and nano-fillers like ZnO, cellulose derivatives, or CQDs into the starch matrix. In CQD-reinforced starch films uniformly dispersed via ultrasonication, water- vapor permeability decreases by 20–30 %, while water-contact angles increase significantly. Optically, these composites maintain over 85 % transparency in the visible region and exceed 90 % UV-blocking capacity. Photoluminescence measurements under 350 nm excitation reveal strong blue emissions around 450 nm, offering the potential for smart packaging and anti-counterfeiting applications. Although CQD additions did not enhance tensile strength compared to pure starch films, they increased elongation at break, improving flexibility. Consequently, these films—insufficient for single-layer packaging—are recommended as functional interlayers in multilayer packaging systems. In this study, blue-fluorescent CQDs with approximately 70 % quantum yield were synthesized via the hydrothermal treatment of a citric acid and ethylenediamine mixture. These CQDs were then incorporated at loadings of 0.1–1 wt % into an optimized (36.4 wt % glycerol) starch–glycerol matrix, producing homogeneous thin biocomposite films via solution casting. The chosen base starch film (Film C) exhibited the most balanced hydration and visual characteristics. FT-IR analyses revealed intensity decreases at 925 cm⁻¹ and 1721 cm⁻¹ bands, indicating hydrogen- bond interactions between CQDs and starch chains. Photoluminescence studies showed strong blue emission at 445 nm with an approximate quantum yield of 70 %. Barrier testing demonstrated that CQD-reinforced films significantly reduced water- vapor permeability and moisture uptake as CQD content increased. For instance, C- CQD-0.5 and C-CQD-1 samples exhibited 35-40% and 55-70% lower water-vapor permeability compared to the pristine starch film, respectively. Water-vapor sorption tests at 58 % and 99 % relative humidity confirmed consistently lower moisture uptake across all CQD-filled films. Water-contact-angle measurements showed marked increases in surface hydrophobicity for films with 0.5–1 wt % CQD, minimizing water–surface interaction. Mechanical characterization, including tensile strength and elongation at break, revealed that CQD addition did not significantly improve tensile strength but increased elongation by 20–35 %, indicating enhanced flexibility. These findings suggest that CQD-reinforced films, while flexible, lack sufficient strength for standalone use and are therefore suited as intermediate layers in multilayer packaging systems. Optical analyses confirmed that the composites maintain over 85 % transparency in the visible range and block 70–90 % of UV-A, UV-B, and UV-C radiation, thus preserving product visibility and preventing photodegradation. The photoluminescence performance provides direct visual cues for smart-packaging applications. In moisture-uptake, solubility, and long-term durability tests, the C-CQD-0.5 formulation stood out: its 24-hour solubility was measured at 36.6 ± 0.6 %, and at 28 days it remained at 30.8 ± 0.8 %, compared to 42.8 ± 1.6 % and 37.0 ± 2.4 % for the pure film. These results indicate that CQDs densify the matrix, reducing water interaction and preserving structural integrity in humid environments. In conclusion, starch–glycerol films containing 0.5–1 wt % CQDs exhibit the most balanced barrier, optical, and photoluminescent performance. The data demonstrate that these formulations are strong candidates for eco-friendly, biodegradable, and multifunctional food packaging materials. Future work should involve shelf-life studies incorporating antimicrobial and antioxidant additives, scaling up production, and conducting cost–sustainability analyses to enable the commercial deployment of ecological and functional food-packaging alternatives to petroleum-based plastics.
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ÖgePolyamide synthesis for reverse osmosis membrane and substrate optimization(Graduate School, 2024-02-02)Because of growing population, global warming and increasing industrialisation, our need for clean water is growing. Water treatment systems can be used to treat industrial wastewater, sewage, etc., as well as sea water, and turn it into drinking water. There are many systems for purifying water. Nanofiltration, microfiltration, reverse osmosis, forward osmosis, and electrodialysis are the most common. 60% of the world's water purification systems are RO. In addition, the use of polymer membrane is common. In general, the RO membranes work under the press, which is able to change the pressure from 60 bar up to 100 bar. Reducing energy consumption is the most issue in RO research due to the high pressure. The cost of RO systems can be reduced by reducing the amount of pressure applied. When the amount of pressure applied is reduced, cost effectiveness is achieved. Reverse osmosis is the process by which water is desalinated using membranes that separate the dissolved components in the feed water but allow the water to pass through. In the reverse osmosis membrane process, as water passes through a membrane by the solution-diffusion mechanism, solutes are retained by electrostatic forces in their size and dissolved ions on the membrane surface. Polymeric RO is composed of three layers. The firs layer, a thin film, which is made up of polyamide separates the components like salt ions. The second layer, a porous polysulfone support layer, directs the flow of water. The final layer, a nonwoven PET layer, increases mechanical strength. Polysulfone carrier layers can be produced by electroblowing, electrospinning or solution blowing. The support layer produced by nanofiber production methods generally has a more porous structure. The nanofiber support layer leads to useful way by which the water flux conveniently pass through, contrast to other support layer types. This results in a high water flow and a reduction in the required applied pressure. This situation reduced energy concuption. The supporting layers made by the phase inversion method have a low percentage of the surface voidand the void size on the surface is relatively small compared to the others support layer types made by nanofiber production methods. The advantage of the phase inversion method is that is more suitable for industrial production. The reasons for the selection of nanofiber production by electro-blow spinning method are that the fiber optimization process is relatively easier and it is also efficient in mass production.
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ÖgeImprovement of electrical and photocatalytic properties of boron-doped ZnO nanorods and synthesis design optimization by taguchi approach(Graduate School, 2024-01-29)Today, increasing environmental pollution affects the whole world. One of the most important pollutions among environmental pollution is water pollution. Water pollution seriously threatens living life. With the developing technology, clean water resources are decreasing, and water resources are polluted with industrial and domestic wastes every day. Today, traditional methods are used for water treatment. However, these methods are not able to provide adequate response to water treatment due to low efficiency for small-sized pollution and secondary pollution. Therefore, applications of photocatalysis offer an effective opportunity among advanced oxidative methods; in this study, innovative photocatalyst structures have been developed. Boron doped ZnO nanorods were successfully synthesised by hydrothermal method and Boron doping has led to enhancements in its photocatalytic and electrical properties. Boron doped ZnO nanorods were grown in two stages. In the first stage, since dipole forces will be effective for growth, the thin film called seed layer layer on the glass surface was coated with the surface spin coating method. Then, with zinc nitrate dehydrate and hexamethylenetetetraamine added in equal molar amounts, nanorods were grown on the glass with seed layer at 90 °C for 3 hours. X-ray diffaraction (XRD), UV-Vis spectrometer, FT-IR, DC electrical analysis (I-V), AC electrical analysis, characterisation by Scanning electron microscopy (SEM) and photocatalytic analysis by UV-A 366 nm light were also performed. Then, Taguchi experimental design method was used to determine the best conditions for selected parameters such as pH, pollutant concentration, time, additive amount and to calculate the effects between each other. The XRD results indicate that boron has successfully integrated into the structure. Also, pure and boron doped ZnO nanorods grew in wurtzite structure and the crystal sizes were confirmed by SEM images. As a result of FT-IR analysis, it was shown that the peak belonging to B-O, B-O-B bonds increased with the increase in doping. It was proved that the band gap intervals calculated as a result of UV-Vis spectrometry analysis decreased with boron doping. Electrical analyses showed that the electrical conductivity increased with increasing boron doping. As a result of all these analyses, electrical conductivity increased from 0.03 μA for pure ZnO to 1.9 μA for 10% boron doped ZnO. With the increase in surface defect, the band gap decreased with the increase in conductivity, boron doping was proven to increase the number of electrons and it was thought that their photocatalytic activity should increase. As a result of photocatalytic tests, it was shown that the efficiency increased with boron doping. When we compare the numerical values of the rate constants, under the same conditions, the 1% B doped sample has a 94% higher rate than the pure ZnO sample for pH 4. For pH 7, the 3% B-doped sample has a 36% higher rate than pure ZnO, and finally for pH 10, the 7% B-doped sample has a 194% higher rate constant. Moreover, the effect of pH was discussed. It was observed that boron doped ZnO nanorods had better photocatalytic efficiency for each pH range and concentration. As a result of the calculated rate constants, 3% boron doping for 2x10-6 M concentration, pH 7 showed the best result with a rate constant value of 0.00856 min-1. Finally, optimized parameters for pH 4, concentration 2x10-6 M, time 90 min and doping amount 7% were determined by Taguchi method. As a result of ANOVA analysis, the model was proved to be 85% fit.
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ÖgeComparison of naproxen-loaded zeolitic imidazolate frameworks (ZIF) and halloysite nanotube-zif composites with 3D printed PLA embedded in gelatin hydrogel(Graduate School, 2024-07-17)Nanomedicine is an interdisciplinary discipline that integrates nanotechnology with biomedical sciences. It brings about a revolution in illness management by introducing revolutionary methods in diagnosis, treatment, and prevention. A crucial element of this development is the investigation of nanocarriers, vital constituents in sophisticated pharmaceutical delivery systems that aim to surpass biological obstacles and facilitate precise and regulated drug discharge. Within this framework, the study specifically examines two types of inorganic nanocarriers, namely Zeolitic Imidazolate Frameworks (ZIFs) and Halloysite Nanotubes (HNTs). These two nanocarriers possess similar distinctive characteristics, which make them well-suited for a comparative analysis. ZIFs, which are categorized as metal-organic frameworks (MOFs), possess a wide range of beneficial characteristics that are essential for their function as nanocarriers in nanomedicine and drug delivery systems. The characteristics of these materials encompass high porosity, modifiable size and structure, convenient surface alteration, minimal toxicity, significant loading capacity, improved stability, favorable biocompatibility, water solubility, and biodegradability. ZIFs exhibit pH-responsive properties, allowing for the targeted release of medications in response to changes in acidity. This attribute improves the accuracy and timeliness of drug administration. In comparison, Halloysite Nanotubes (HNTs) belong to a different category of inorganic nanocarriers that offer exceptional characteristics, making them extremely desirable for use in medicinal applications. The inherent tubular morphology of HNTs enhances their biocompatibility, extensive surface area, and capacity for surface modification, making them highly favorable for applications as drug delivery systems. HNTs possess the ability to release drugs in a controlled and prolonged manner, while also having less toxic effect and being naturally abundant. This makes them highly adaptable and beneficial in the field of pharmaceutical sciences. Furthermore, HNTs possess antibacterial properties, which are essential in situations when it is necessary to prevent the growth of germs. The pH-responsive drug release properties of HNTs further facilitate accurate and focused medication delivery. Therefore, HNT- ZIF combination was designed and synthesized to analyze how the properties of HNT effect the properties of ZIF, comparing with synthesized ZIF. Hydrogels that are known for their capacity to absorb water and compatibility with living organisms and are crucial in the field of biomedicine, particularly in applications such as wound dressings and drug delivery systems. The scaffold structures used in tissue engineering, particularly when paired with poly(lactic acid) (PLA), play a significant role in promoting cell proliferation and tissue regeneration. PLA offers advantages such as providing structural reinforcement and undergoing a progressive process of biodegradation. The combination of hydrogel and PLA scaffold, facilitated by 3D printing technology, improves accuracy and personalization. The benefits of utilizing 3D printing in tissue engineering encompass the capacity for replication, expandability, and the capability to fabricate structures with regulated porosity. The combination of these elements has the potential to generate groundbreaking solutions in the field of regenerative medicine. The aim of the study was to combine two distinct patches: one comprising a composite gelatin hydrogel and PLA scaffold with Naproxen, a nonsteroidal anti-inflammatory drug, loaded ZIF embedded within it, and the other comprising a composite gelatin hydrogel and PLA scaffold with Naproxen loaded HNT-ZIF embedded within it. The objective is to evaluate and compare the drug loading capacity, drug release behavior and pH responsiveness To determine their properties using various techniques, including scanning electron microscopy (SEM), Liquid Chromatography–Mass Spectrometry (LC-MS), Energy-Dispersive X-Ray Spectroscopy (EDS), swelling capacity determination, drug release analysis, pH responsiveness analysis, and in vitro cytotoxicity study. They were successfully completed. Based on examinations, ZIF and HNT-ZIF composite were synthesized successfully and their bonds and each size of synthesized nanoparticles were quite similar with literatures, which FT-IR graphs and SEM images proved. Data of EDS and FT-IR demonstrates that Naproxen was loaded into synthesized nanocarriers and according to LC-MS results show approximately %92 efficiency. Drug release and pH responsiveness analysis demonstrates HNT-ZIF had lower release rate and both HNT-ZIF and ZIF were pH responsive. Additionally, SEM images show that gelatin hydrogel has too small pores and polymer layers. Moreover, swelling capacity of PLA embedded gelatin hydrogel was quite stable due to strong mechanical properties of PLA. The results of toxicity shows that HNT may contribute to increased cell viability in HNT-ZIF due to block the release of ions from organic linkers of ZIF. In high concentration of ZIF, cell viability was higher than followed decreased concentration with 1:2 dilution due to the fact that it was agglomerated. In lower concentration, especially 0.0025 mg/µL, there could be more released ZIF without agglomeration. Moreover, the incorporation of hydrogel nanocarrier composites significantly enhances cell viability compared to samples lacking hydrogels. This demonstrates that hydrogel effectively slows down the release of ions and drugs.
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ÖgeDesigning, developing and using the anode of a microbial fuel cell by containing PDMS,carbon nanotubes and graphene(Graduate School, 2022)In the last few years, micro/nano electromechanical systems are an area that has been rising very rapidly and attracting a lot of attention of researchers. Microbial fuel cells, which is also a subject covered by the MEMS/NEMS field, is also a very interesting field of study. The reason for this is the increase in energy consumption in the world with each passing day and the search for a renewable energy source has become a necessity. The anodes and cathodes of MFCs are intended to operate at both low cost and high efficiency. Graphene, carbon nanotubes and PDMS, an organic polymer, can be counted among the materials that are widely used in this field and are trying to be developed. In our own study, we used these materials as hybrid nanocomposites. In addition to the MFC anode electrode studies in the literature, we tried to obtain electrical conductivity with lower cost and higher efficiency. In order to achieve these goals, we designed a special pattern in the anode electrode, which will increase the electrode surface area in a way that the microbial flora can be used most effectively, ensure the efficient adhesion of the microbial flora, and to attract electrons with the highest capacity, and we have produced it by photolithography. In order to find the optimum electrode, PDMS/MWCNT/GNP hybrid nanocomposite samples were produced at different ratios. In addition, the effect of treating the produced anode electrodes with sulfuric acid on the electrical conductivity was investigated. As a result of our production, we analyzed the anode electrodes with a few characterization devices that are widely used in nanotechnology studies. As a result of the analyzes made, it was observed that the produced electrodes had a very successful electrical conductivity when compared with the examples in the literature. It has been observed that the treatment with sulfuric acid causes a very successful increase in electrical conductivity within a certain treatment time. As an important result, it has been observed that the electrical conductivity can vary greatly depending on the mixing ratios and the type of nanofiller used. As a result of this experimental study, it has been concluded that the electrodes produced at low cost and at certain rates have successful electrical conductivity compared to previous studies in the literature.