| Quantum dots (QDs), also known as semiconductor nanocrystals, are under heavy investigation due to their unique optical properties. Compared with traditional fluorescent materials, QDs has many advantages such as high photostability, longer fluorescence lifetime, broad absorption, and narrow emission with peak position tunable by their sizes. QDs have potential widespread applications in many fields such as biology, environment & energy, security and electronic. Wet-chemical synthesis of QDs can be generally divided into water-phase and organic-phase methods. Compared with organic-phase method, synthesis in aqueous system is relatively easier, cheaper, less toxic and more ecofriendly. More importantly, the products usually show good water-solubility and biocompatibility. Due to these advantages, synthesis of QDs in water solution has attracted more and more attention. However, the quality of QDs in water-phase is still required to be improved. To solve the problems in synthesis of QDs in water, we try to fabricate a composite of CdTe QDs with polymer. Bacterial cellulose (BC) is known for its natural origin and unique properties and structures such as good biocompatibility, high crystallinity, ultrafine nano-sized three-dimensional fibrous network structure and excellent mechanical strength. There are also many hydroxyl groups on the nanofibers. These properties make BC as a good template or matrix for the synthesis of QDs. In this paper, we reported a simple and economical method to synthesize CdTe QDs in water, and use BC as template to fabricate CdTe/BC nanocomposites. Moreover, the nanocomposites can be used as a kind of Cu2+ ion test paper, which has a good selectivity and detectability for Cu2+. The major works are shown as follows:(1) At first we improved the synthesis of CdTe QDs in water. Na2TeO3 was adopted instead of Te, the TGA and NaBH4 was also used. During the synthesis, no N2 protection is needed. Through controlling the reaction time, we can get QDs with different fluorescence colors. The as-prepared QDs were characterized by TEM and PL spectra, the results show that the morphology and fluorescence property is still required to be improved.(2) Color-tunable luminescent membranes based on bacterial cellulose (BC) were successfully fabricated by the in situ synthesis of the CdTe QDs on the BC microfibrils in aqueous solution. The membranes can emit fluorescence with high brightness and homogeneity.The micro structure of samples was studied by XRD, FESEM-EDS and TEM. The results show that the shape of QDs was improved and the size distribution were narrower. The optical properties were studied by PL spectra and UV-vis spectra, the results show that the properties and stability of QDs were improved when BC matrix exsited. The TG and mechanical measurements also confirmed that the membranes can maintain the properties of BC.(3) We use the fluorescence quenching effect to make the luminescent membranes as Cu2+ ion test paper. In the selectivity experiments, we found that the membranes have good selectivity to Cu2+ ion and the green luminescent membranes show the best selectivity. We also established the quenching equation of the membrane:F0/F=1+0.0028585C (C=10-6mol/L), the quenching constant K=2.858 X 103L/mol, the detection limit is 0.016 mM. The mechanism was also explored by XPS. |
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