| Summary: | 博士 === 國立成功大學 === 化學系 === 106 === The optical nanoprobes made up of nanomaterials with recognition units, have the optical signal intensity vary depended on the concentration of the analyte(s). Materials reducing the size or length between 1nm and 100 nm can exhibit a size-related property that is quite different from macroscopic scales, such as the localized surface plasmon resonance(LSPR) or the fluorescence. Noble metal nanoparticles(NMPs), such as gold(Au) and silver(Ag), possessing the SPR frequency can absorb the wavelength between 200nm and 800 nm (UV-Vis range), have been developed as a colorimetric probe for detection of heavy metal or small organic molecule.
Tartrate-capped silver nanoparticles modified by cetyl trimethyl ammonium (CTA-TA/Ag NPs) were synthesized via one pot synthesis and confirmed by transmission electron microscopy, IR spectrometry, and Dynamic Light Scatter. CTA-TA/Ag NPs can redox with mercury ion (Hg2+) and hexavalent chromium (Cr6+) at around pH 2. While Cr6+ devastated Ag NPs via the redox reaction, the Ag NPs will vanish and result in diminishing of the LSPR absorption. When Ag NPs were oxidized by Hg2+, it is not only etched but also formation of Hg0-Ag nanoalloy on the Ag NPs surface. This kind of reaction will reduce the particle size and cause the blue shift of the LSPR absorbance. Comparing the LSPR change of CTA-TA/Ag NPs mixed with other 13 common ions, the selectivity is excellent for Hg2+ and Cr6+. While the sample solution mixed with vitamin C, the probe is specifically to detect Hg2+. The detection limit of Hg2+ and Cr6+ ions are 0.08 μM and 0.15 μM, respectively. The linearity is ranging from 0.25 μM to 3 μM for Hg2+ and from 0.2 μM to 17.5 μM for Cr6+.
On the other hand, carbon nanodots (CDs) modified with ethylene diamine and the amino acids (AAs) Cys, His, Lys or Arg were synthesized by one pot procedure, and their structures were confirmed by high resolution transmission electron microscopy, Raman spectrometry, and X-ray photoelectron spectrometry. It is found that derivatization the N-doped carbon dots with various AAs systemically modulates their electronic properties, and this results in a tunable selectivity in detection of metal cations via fluorescence quenching. The assays can be performed in aqueous solutions at near-neutral pH values. The drop of fluorescence is directly proportional to the concentration of metal cations in the 1 to 100 ppb range, and the limits of detection are 20.5 ppb, 10.2 ppb, 8.8 ppb, 24.6 ppb, 2.3 ppb, respectively, for Hg(II), Cu(II), Zn(II), Fe(III), and Cr(III).
Both Ag NPs and CDs based probes can be applied to detection of heavy metals in the water sample. CTA-TA/Ag NPs can effectively distinguish Cr6+ from Cr3+. Moreover, the Ag NPs can singlely detect Hg2+ when vitamin C was pre-mixed. It turns to a powerful tool for judging the product wether containing the hazard element, Cr6+ and Hg2+, or not. In the other word, the AA-modified CDs with the different fluorescence response can be converted to logic gates and applied to photoelectronic nanoprobes by using microprocessors. This assay has a large potential in terms of high-throughput screening for trace amounts of metal ions.
|
|---|
