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Polyhedral Oligomeric Silsesquioxanes based Materials as Sorbent and Sensor

Soufi, Gohar | 2023

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 55791 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry
  6. Advisor(s): Bagheri, Habib; Jamali, Sirous
  7. Abstract:
  8. The main approach in this thesis is the synthesis and identification of polyhedral oligomeric silsesquisans (POSS) and their modification with suitable functional groups to induce desired properties and use them as adsorbents or sensor. In the first work, POSSs were used as three-dimensional porous compounds with special properties as extractant phase in solid phase croextraction. Selective extraction of polar and non-polar molecules to particle size and functional groups on POSS. In this research, a threedimensional network of POSS including naphthalene diimide (POSS-NDI) and perylene diimide (POSS-PDI) as an extractant phase capable of absorbing volatile organic compounds was used to analyze lung cancer markers. used. The synthesized diamide was successfully identified by FT-IR, NMR, SEM, TEM, TGA and BET analysis. After optimizing all effective parameters on absorption and desorption, merit figures were obtained for three aldehydes as an indicator of lung cancer in human breath. The exhaled air of twelve volunteers, including seven healthy volunteers and five sick volunteers, was examined. The use of partial least squares discriminant analysis (PLS-DA) led to the appropriate classification of healthy and sick people, and the R2 of its calibration and cross-validation was 0.9733 and 0.7882, respectively . In the second work, a POSS-based sensor was designed to enable rapid and selective detection of aniline vapor and its derivatives. In this work, POSS was synthesized with an amine group and POSS dimer with perylene bridge was synthesized with two morphologies, cubic and amorphous. This compound was fully characterized in solution by multinuclear NMR and also in gas state by ESI-MS. Surprisingly, solid state characterization revealed an unusual cubic morphology with particle dimensions of 160-80 nm. Fluorescence studies show that the bulky POSS units effectively prevent perylene aggregation leading to quenching and subsequently provide a quantum efficiency of up to 92%. Exposure of the sensor to aniline and orthotoluidine results in highly reproducible, reversible, and selective fluorescence quenching responses. For the developed sensor, LoDs of less than 19 and 8 ng/L and linear ranges of 350-65 and 450-25 ng/L were obtained for aniline and O-toluidine, respectively. Mechanistic studies confirm photoinduced electron transfer (PET) as the main pathway responsible for fluorescence quenching . In the third work, a new network based on carbon nanotubes (CNT) and POSS as crosslinkers was synthesized and identified to prepare a universal adsorbent with the aim of removing pollutants from the aquatic environment. This modification improves the trapping of the target (between holes) and increases the polarity and ionic interaction to increase the removal efficiency of ionic and polar species. In order to confirm the synthesis, FT-IR, SEM, TEM, EDX-map, EDS, BET and TGA were used. Therefore, two model analytes with completely different physiochemical properties including difenzocate (DFQ) and pyrene (PYR) were selected. The results show that the removal efficiency of both target analytes after optimization was higher than 99% without adding surfactant. In addition, the adsorption equilibrium isotherms for both PYR and DFQ model analytes were in good agreement with the Freundlich isotherm model, which indicates the role of multilayer adsorption. According to the investigation of absorption kinetics, a higher regression coefficient was obtained for the pseudo-second order to remove DFQ, while for PYR, the pseudo-first-order equation has a higher regression coefficient value. The obtained results show that the adsorption process of DFQ and PYR in CNT-POSS is carried out by two different mechanisms
  9. Keywords:
  10. Environmental Pollutant ; Adsorbent ; Biomarker ; Solid Phase Microextraction ; Polyhedral Oligomeric Silsesquisans ; Naphthalene Diimide ; Perylene Diimide

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