Sıvı petrol ürünleri içerisinde dayanımlı, aşırı-küçük yakın kızılötesi ışıyan kolloidal pbs ve pbs/cds kuantum noktaların geliştirilmesi

Semiconductor nanocrystals (quantum dots) attract significant interest due to their size-dependent optical properties, that are not achievable with the bulk semiconductor materials. Strong luminescence, broad absorption and narrow emission allows excitation of different QDs at a single wavelength, hence allows detection of different QDs at the same time. This unique property is exploited for optical tagging, diagnostic imaging and optical barcode generation. Lead sulfide (PbS) QDs are popular QDs for biological imaging, photovoltaics and LEDs, due to strong absorbance in the visible range and strong emission in the near infrared region (NIR). NIR QDs in biological applications are valuable since excitation can be done in the non-harmful visible wavelength range and emission in the NIR can eliminate the auto-fluorescence of the tissue. It is also possible to generate optical barcodes with NIR QDs, as well, which may be considered as invisible barcodes.to the naked eye. In spite of the high popularity of PbS, its stability is a major problem. Most PbS QDs are large nanocrystals with emission above 1100 nm. Besides, there is only a limited amount of reports on small colloidal PbS in the literature. In this thesis work, development of highly stable, monodisperse, bright PbS and PbSe, and PbS/CdS core-shell QDs with emission between 800-1100 nm was aimed. This range is critical to many applications since most available and inexpensive detectors, such as extended Si-detector do not perform at longer wavelengths. Our application contains use of liquid petroleum products, these have strong and broad auto-fluorescence at 700 nm. So, developing QDs stable in liquid petroleum products with low concentration (100 ppm level) up to a year is the primary aim of this work. Both optical and colloidal stability is needed for the application. Moreover, synthesis of these QDs should be easy, scalable and preferable green synthesis. So, expensive, oxidative, high toxic precursors and processes is inapplicable for the project. In addition to develop these QDs, new synthesis method and coatings were developed and post-processes were improved to satisfy stability and optical requirements of the project.