الفهرس 
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Abstract
In the current thesis, various CDs have been synthesized, characterized, and used to establish spectrofluorimetric analytical methods for selected non-fluorescent drugs. The thesis is composed of five chapters: Chapter I: Introduction This chapter provides a general introduction on CDs, their synthesis and modification strategies, techniques used for their characterization, their PL properties, different quenching mechanisms and a summary of their applications in analytical chemistry. Chapter II: N-doped Carbon Dots as a Fluorescent Nanosensor for Determination of Colchicine Based on Inner Filter Effect This chapter includes a brief introduction on COL, its chemical and physical properties, and presents a review of literature on the analytical methods recently reported for its assay. Furthermore, a novel and simple fluorescent CDs-based nano-sensor for COL determination has been prepared. The CDs probe was prepared using uric acid as a carbon and nitrogen source via a one-step thermal decomposition. The sensor was based on IFE where COL acted as a powerful absorber that affected the excitation of CDs. This overlap resulted in a quantitative attenuation of the fluorescence of CDs with increasing COL concentration in the range of 2–25 μM. The developed sensor had the advantages of simplicity, less time-consumption, convenience, and satisfactory selectivity for COL. The method reached a DL of 0.623 μM and was successfully applied for COL determination in commercial tablets and effervescent granules with mean 153 % recoveries of 102.9% and 104.3%, respectively. This method was published in Journal of Fluorescence, 31 (2021) 675-684. Chapter III: Rapid Microwave Synthesis of N,S-doped Carbon Dots as a Novel Turn Off-On Sensor for Label-free Determination of Copper and Etidronate Disodium This chapter gives a concise introduction on Cu2+ and ETD, their chemical and physical properties and presents a review of literature on the analytical methods recently reported for their assay. Moreover, an environmentally-friendly, selective and rapid turn off-on fluorescent probe for both Cu2+ and ETD detection was derived based on N,S-CDs. The N,S-CDs were produced, for first time, through microwave-assisted pyrolysis in only 60 s using readily accessible and cheap precursors (CA and TSC). The proposed synthesis method resulted in N,S-CDs with narrow particle size distribution, high product yield (64.38 wt%) and high doping efficiency (N, 28.56% and S, 8.47%). The turn off-on sensor was developed after demonstrating the ability of Cu2+ to quench fluorescence of the produced CDs and probable fluorescence restoration through complexation of Cu2+ by the bisphosphonate group of ETD. The developed sensor showed a good performance for Cu2+ and ETD detection with a linear range of 5-125 M and 30-210 M, respectively. The sensor reached a DL of 1.326 M for Cu2+ and 8.592 M for ETD. This developed platform was applied successfully for analysis of Cu2+ in river water and ETD in pharmaceutical preparation with mean % recoveries of 93.3% and 97.5%, respectively. This method was published in Analytica Chimica Acta, 1197 (2022) 339491. : Innovative Spectrofluorimetric Determination of Vildagliptin Based on a “Switch Off-On” N,S-doped Carbon Dots Nanosensor This chapter delivers a summarizing introduction on VLD, its chemical and physical properties and presents a review of literature on the analytical methods recently reported for its assay. In addition, a rapid, simple and selective switchable sensor based on the as-prepared N,S-CDs for the determination of VLD without requiring any chemical reagent was developed. The sensor was based on quenching the fluorescence of N,S-CDs with Cu2+ through complexation with the functional groups present on N,S-CDs surface and then recovering the fluorescence using VLD’s ability to complex Cu2+. The developed probe (N,S-CDs/Cu2+) demonstrated a good sensing performance for VLD with linearity from 45-240 M and DL of 13.411 M. This designed sensor was successfully applied for determination of VLD in commercial tablets with mean % recovery of 99.5% and in human urine samples with % recoveries from 98.4% to 101.6%. This method was published in RSC Advances, 12 (2022) 25815- 25821. Chapter V: Microwave Synthesis of N and S Co-doped Carbon Dots as a Novel Fluorescent Sensor for Determination of Tilmicosin This chapter gives a short introduction on TLM, its chemical and physical properties and presents a review of literature on the analytical methods recently reported for its assay. In addition, an eco-friendly, selective, and rapid fluorescent probe for TLM detection was derived based on GLCY-CDs. The GLCY-CDs were produced, for first time, through microwave-assisted pyrolysis in only 90 s using readily accessible and cheap precursors (glucose and L-cysteine). The proposed synthesis method resulted in GLCY-CDs with narrow particle size distribution, high product yield (50.25 wt%) and successful doping (N, 2.01% and S, 1.88%). The sensor was based on dynamic quenching mechanism that involved collision between TLM and the excited state of CDs causing its return to the ground state and quenching of fluorescence. The developed sensor showed a good performance for TLM detection with a linear range of 9-180 M and DL of 1.903 M. This developed sensor was applied successfully for analysis of TLM in pharmaceutical formulation with mean % recovery of 99.7% and in milk with mean % recoveries from 98.5% to 101.7%. This thesis contains 33 tables, 59 figures, 4 schemes, and 242 references in addition to summary and summary in Arabic.