University of Connecticut OpenCommons@UConn Master's Theses University of Connecticut Graduate School 5-11-2016 Fluorescent Carbon Nanoparticles for Sensitive and Selective Detection of Palladium (Pd2+) Sichen Zhang [email protected] Recommended Citation Zhang, Sichen, "Fluorescent Carbon Nanoparticles for Sensitive and Selective Detection of Palladium (Pd2+)" (2016). Master's Theses. 929. https://opencommons.uconn.edu/gs_theses/929 This work is brought to you for free and open access by the University of Connecticut Graduate School at OpenCommons@UConn. It has been accepted for inclusion in Master's Theses by an authorized administrator of OpenCommons@UConn. For more information, please contact [email protected]. Fluorescent Carbon Nanoparticles for Sensitive and Selective Detection of Palladium (Pd2+) Sichen Zhang B.S., Hefei University, 2011 A Thesis Submitted in partial Fulfillment of the Requirement for the degree of Master of Science At the University of Connecticut 2016 Copyright by Sichen Zhang 2016 ii APPROVAL PAGE Masters of Science Thesis Fluorescent Carbon Nanoparticles for Sensitive and Selective Detection of Palladium (Pd2+) Presented by Sichen Zhang, B.S. Major Advisor____________________________________________ __ Yu Lei Associate Advisor____________________________ _______________ Christian Bruckner Associate Advisor_________________________________ __________ Guoan Zheng University of Connecticut 2016 iii Acknowledgement I would like to express my deepest appreciation to my major advisor, Professor Yu Lei, for his guidance and continuous support in my master’s period. I have gained a lot of experience on research and life under his supervision. Furthermore, I would like to thank my co-advisors, Professor Christian Bruckner and Professor Zheng Guoan. They have provided constructive suggestions and insightful advices to help me to complete my program. I want to take this opportunity to thank Professor Hong Chen, who granted me the knowledge of organic chemistry and initiated my interest for further education. In the two past years, my dealing labmates, Dr. Xiangcheng Sun, Jun Chen, Xiaoyu Ma, Qiuchen Dong, Rafaela de Silverira and Dongwook Kawa have shared their experience on research and helped me a lot in the daily life. I also would like to appreciate Professor Jie He and Junkai He for their assistance for the characterization techniques and analysis. Finally, I would like to thank my parents and my friends. Without their unlimited love and support, I cannot realize my dream for master degree. I also want to thank Yang for his help and companionship. iv Contents APPROVAL PAGE ........................................................................................................................................... iii Acknowledgement .......................................................................................................................................... iv Abstract ............................................................................................................................................................ vii 1. Introduction ............................................................................................................................................... 1 1.1. Fluorescent carbon nanoparticles and their preparation methods and applications ....... 1 1.1.1. Fluorescent carbon nanoparticles .................................................................................... 1 1.1.2. Preparation methods of carbon nanoparticles ............................................................... 2 1.1.3. Applications of CNPs ....................................................................................................... 11 1.2. Palladium and its applications .................................................................................................... 28 1.3. Fluorescence-based palladium sensing .................................................................................... 29 1.4. Objective of thesis ........................................................................................................................ 30 2. DESIGN OF CNPs-BASED FLUORESCENCE PROBE FOR PALLADIUM SENSING ................. 31 2.1. Preparation methods of CNPs .................................................................................................... 31 2.2. The design of CNPs-based fluorescence chemosensor for Pd2+ sensing ........................... 31 3. MATERIALS AND METHODS ................................................................................................................. 33 3.1. Reagent and chemicals ............................................................................................................... 33 3.2. Preparation of fluorescent carbon nanoparticles ..................................................................... 33 3.3. Characterization ............................................................................................................................ 34 3.4. Detection of Pd2+ in the aqueous phase ................................................................................... 34 4. RESULT AND DISCUSSIONS .................................................................................................................. 36 4.1. Morphology and characterizations of CNPs ............................................................................. 36 4.1.1. High resolution of TEM ............................................................................................................. 36 4.1.2. X-ray diffraction pattern ............................................................................................................ 37 4.1.3. Fourier transformed infrared spectrum .................................................................................. 37 4.1.4. X-ray photoelectron spectrum ................................................................................................. 38 4.2. Optical property of CNPs ............................................................................................................. 40 4.2.1. Excitation and emission spectrum .......................................................................................... 40 4.2.2. Photographs of the CNPs excited by LEDs .......................................................................... 41 4.2.3. UV-vis absorption spectrum .................................................................................................... 42 4.2.4. Emission scan spectrum .......................................................................................................... 43 4.3. Quantitative analysis and selective detection of Pd2+ ............................................................. 44 v 5. Conclusion ...................................................................................................................................... 48 6. Outlook ......................................................................................................................................................... 49 7. References .................................................................................................................................................. 51 vi Abstract Fluorescent carbon nanoparticles (CNPs) was synthesized using well-known citric acid and polyethylenimine precursors but under a modified microwave reaction conditions in order to achieve high sensitivity and selectivity for Pd2+. The as- synthesized fluorescent CNPs with an average diameter of 2-3 nm exhibited good water solubility and photo-stability. The CNPs were systematically characterized using various advanced techniques and the fluorescence study on the as-prepared CNPs showed the excitation-dependent emission properties. Finally, the as-synthesized carbon nanoparticles served as a promising fluorescence probe for Pd2+ sensing. The sensitivity and the selectivity for Pd2+ detection were investigated by fluorescence quenching titrations and comparison of various competing metal ions, respectively. The results show that besides the excellent selectivity to Pd2+ against other metal ions, the limit of detection to Pd2+ could also reach as low as 12.4 nM, which is much lower than the threshold concentration limit of Pd2+ in medicine and environmental samples. The findings here indicate that the as-prepared CNPs hold great promise as a low-cost sensing material for sensitive and selective detection of palladium. Keywords: Fluorescent carbon nanoparticles, Sensitivity, Selectivity, Limit of detection, Fluorescence probe. vii 1. Introduction 1.1. Fluorescent carbon nanoparticles and their preparation methods and applications 1.1.1. Fluorescent carbon nanoparticles Carbon nanomaterials including carbon nanotubes, graphene sheets, nanodiamonds, fullerenes and fluorescent carbon nanoparticles have attracted much research interest in recent years. Especially, carbon nanoparticles (CNPs), because of their excellent optical properties, biocompatibility, water solubility, photo-stability, and ease of cost-effective synthesis, have gained tremendous attention in a wide spectrum of chemical and biomedical applications, ranging from sensing to bioimaging, fluorescent ink and phototherapy. In recent years, fluorescent CNPs have been regarded as a promising candidate to replace the conventional semiconductor quantum dots in various applications 1. Fluorescent CNPs were coincidentally discovered and produced in the process of purification of single-wall