Studying The Interaction Between CdX (X=Se, Te) Quantum Dots And Chitosan, Chymotrypsin, Nile Blue And Human Serum Albumin By Resonance Rayleigh Scattering, Absorption And Fluorescence Spectra

During the last two decades, there was an intense scientific and technological interest in studying colloidal semiconductor nanoparticles also called quantum dots (QDs) because of theirs unique excellent optical properties, such as wide absorption and narrow emission spectra, large extinct coefficients, resistance to photobleaching, long fluorescence lifetime, and size-tunable emission. Resonance Rayleigh scattering (RRS) as an analytical technique attracted lot of interests because of its sensitive and simple. In particular, with the rapid development of nanotechnology, great attention has been focused on investgating nanoparticles using the RRS probes, for example, Au nanoparticles, Ag nanoparticles and CdS nanoparticles. However, QDs have unique light scattering signals, and they are likely to be used as effective light scattering emission probes, while presently they were seldom used as RRS probes. CdX QDs (X= Se, Te) were synthesized in aqueous solution, transmission electron microscopy (TEM) was used to observe the appearance and size of nanoparticles. The interaction between CdTe QDs and nile blue (NB) was investigated by ultraviolet-visible (UV-vis) absorption, resonance Rayleigh scattering (RRS) and fluorescence spectroscopy. The obtained results suggested the more satisfactory mechanism for the interaction between CdTe QDs with NB; the interaction between CdSe QDs and chitosan, CdTe QDs and chymotrypsin, human serum albumin was investigated; a method for the determination of chitosan using CdSe QDs as probes was built; the fluorescence quenching mechanism chy and HSA by CdTe QDs was dicussed; binding constant, and thermodynamics parameters during the binding process was obtained.1 Studying the interaction between CdTe quantum dots and nile blue by absorption, fluorescence and resonance Rayleigh scattering spectra Thioglycolic acid (TGA) capped CdTe quantum dots (QDs) with the diameter of 2-3 nm were synthesized. The interaction between CdTe QDs and nile blue (NB) was investigated by UV-vis absorption, resonance Rayleigh scattering (RRS) and fluorescence spectroscopy. UV-vis absorption spectrum of CdTe QDs and NB obviously changed, showing that CdTe QDs could associate with NB to form a new complex. At pH 6.8, NB effectively quenched the fluorescence of CdTe QDs. It was proved that the fluorescence quenching of CdTe QDs by NB was mainly result of the formation of CdTe QDs-NB complex, electrostatic attraction and hydrophobic forces played a major role in stabilizing the complex. The binding molar ratio of CdTe QDs and NB was 5:1 by a mole-ratio method. The interaction between CdTe QDs and NB lead to the remarkable enhancement of RRS and the enchantments were in proportional to the concentration of NB in a certain range. The mechanism of the interaction between CdTe QDs and NB, reasons for the enhancement of RRS intensity were also discussed. The obtained results suggested the more satisfactory mechanism for the interaction between CdTe QDs with NB.2 Study on the interaction between CdSe quantum dots and chitosan by resonance Rayleigh scattering spectraTwo different stabilizing agent thioglycolic acid (TGA) and L-Cysteine (L-Cys) capped CdSe QDs with the diameter of 2 nm were synthesized, large amounts of stabilizing agents connected to CdSe QDs surface through Cd-S bond. The interaction between chitosan and QDs had been investigated respectively. The interaction lead to the remarkable enhancement of RRS, RNLS and the enchantments were in proportional to the concentration of chitosan in a certain range. Under the optimal conditions, compared with TGA-CdSe QDs, the interaction between L-Cys-CdSe QDs with chitosan owned more broad linear range 0.042-3.0 ug mL-1 and lower detect limits 1.2 ng·mL-1. The influences of factors on the interaction between chitosan with QDs and some foreign substances were all examined, which showed that the methods had a good sensitivity and selectivity. Based on this, it is hoped to build a method for the determination of chitosan using CdSe QDs as probes. Through Fourier transform infrared spectroscopy (FTIR) transmission electron microscopy (TEM), it was speculated that CdSe QDs interacted with chitosan to form a network structure aggregates through electrostatic attraction and hydrophobic forces. The reasons for the enhancement of RRS were investigated.3 A study of the interaction between CdTe quantum dots and chymotrypsin by absorption, fluorescence and resonance Rayleigh scattering spectraThioglycolic acid (TGA) capped CdTe quantum dots (QDs) with the diameter of 2-3 nm were synthesized. The interaction between CdTe QDs and chymotrypsin (chy) was investigated by UV-vis absorption, fluorescence and resonance Rayleigh scattering (RRS) spectroscopy. Under pH 7.2, CdTe QDs effectively quenched the intrinsic fluorescence of chy via static quenching. The binding constants for the formation of a complex between CdTe QDs and chy were 2.87,2.83,2.69×103 M"'at 293,298 and 303 K, respectively.△S°and△H°at different temperatures were calculated.△S°(51.12 J·mol-1) and△H°(-4.42 kJ-mol-1) indicated that electrostatic attraction was the dominant intermolecular forces in stabilizing the complex. The interaction between CdTe QDs and chy lead to the remarkable enhancement of RRS and the enchantments were in proportional to the concentration of chy in a certain range. The reasons for the enhancement of RRS were dicussed.4 Studying on the interaction between CdTe quantum dots with human serum albumin by absorption, fluorescence and resonance Rayleigh scattering spectraCdTe quantum dots (QDs) were synthesized in aqueous solution using 2-mercaptoethylamine hydrochloride (CA) as stabilizing agents. The interaction between CA-CdTe QDs with human serum albumin (HSA) was investigated by UV-vis absorption, fluorescence and resonance Rayleigh scattering (RRS) spectroscopy. CA-CdTe QDs could strongly quench the intrinsic fluorescence of HSA by static quenching. The electrostatic interaction plays a major role in stabilizing the complex. The binding site number n and apparent binding constant K, corresponding thermodynamic parameters△G°,△H°and△S°at different temperatures were calculated. The interaction between CA-CdTe QDs and HSA led to the remarkable enhancement of RRS and the enchantments were in proportional to the concentration of HAS. Based on this, RRS methods to determinate HSA were developed. The influences of factors on the interaction between HSA with CA-CdTe QDs and some foreign substances were all examined, which showed that the method had a good sensitivity and selectivity. In addition, the reasons for the enhancement of RRS were investigated.