Synthesis of CdS nanoparticles in colloidal state and its possible interaction with tyrosine

Study on the Interaction between Cadmium Sulphide Nanoparticles and Proteins by Resonance Rayleigh Scattering Spectra

The interaction of cadmium sulphide nanoparticles[(CdS)n]with proteins has been studied by resonance Rayleigh scattering spectra (RRS). Below the isoelectric point, proteins such as bovine serum albumin (BSA), human serum albumin (HSA), lysozyme (Lys), hemoglobin (HGB), and ovalbumin (OVA) can bind withCdSnto form macromolecules by virtue of electrostatic attraction and hydrophobic force. It can result in the enhancement of resonance Rayleigh scattering spectra (RRS) intensity. Their maximum scattering peaks were 280 nm, and there was a smaller peak at 370 nm. The scattering enhancement (ΔIRRS) is directly proportional to the concentration of proteins. A new RRS method for the determination of trace proteins using uncappedCdSnnanoparticles probe has been developed. The detection limits are 19.6 ng/mL for HSA, 16.7 ng/mL for BSA, 18.5 ng/mL for OVA, 80.2 ng/mL for HGB, and 67.4 ng/mL for Lys, separately. In this work, the optimum condition of reaction, the effect of foreign, and the analytical application had been investigated.

Photoinduced Electron Transfer from Meso-Tetrakis (N-methylpyridyl)porphyrin (TMPyP) to Colloidal CdS

A stable colloidal CdS nanoparticles were prepared. The dynamics of photoinduced interaction between meso-tetrakis(N-methylpyridyl)porphyrin (TMPyP) and colloidal CdS were studied using absorption, steady state, time resolved fluorescence and FT-IR spectral measurements. The apparent association constant (K app) of TMPyP-CdS obtained from absorption spectral changes is 1.07×103 M−1. The K app value of TMPyP-CdS as determined from fluorescence spectra is 1.34×103 M−1, which matches well with that determined from the absorption spectra changes. These data indicate that there is an interaction between TMPyP and colloidal CdS nanoparticle surface. The dynamics of photoinduced electron transfer from TMPyP to the conduction band of colloidal CdS nanoparticle has been observed and the mechanism of electron transfer has been confirmed by the calculation of free energy change (ΔG et) by applying Rehm-Weller equation as well as energy level diagram. Lifetime measurements gave the rate constant (k et) for electron injection from the excited state TMPyP into the conduction band of CdS is 3.21×108 s–1.

Biological Synthesis of Size-Controlled Cadmium Sulfide Nanoparticles Using Immobilized Rhodobacter sphaeroides

Size-controlled cadmium sulfide nanoparticles were successfully synthesized by immobilized Rhodobacter sphaeroides in the study. The dynamic process that Cd(2+) was transported from solution into cell by living R. sphaeroides was characterized by transmission electron microscopy (TEM). Culture time, as an important physiological parameter for R. sphaeroides growth, could significantly control the size of cadmium sulfide nanoparticles. TEM demonstrated that the average sizes of spherical cadmium sulfide nanoparticles were 2.3 +/- 0.15, 6.8 +/- 0.22, and 36.8 +/- 0.25 nm at culture times of 36, 42, and 48 h, respectively. Also, the UV-vis and photoluminescence spectral analysis of cadmium sulfide nanoparticles were performed.

Interaction between certain porphyrins and CdS colloids: a steady state and time resolved fluorescence quenching study

The interaction between porphyrins namely, meso-tetrakis (4-methoxyphenyl)porphyrin (TMeOPP), protoporphyrin IX (PPIX) and Zinc(II) meso-tetraphenylporphyrin (ZnTPP) with colloidal CdS has been studied by using steady state and time resolved fluorescence quenching measurements. The porphyrins adsorbed on the surface of colloidal CdS due to electrostatic interaction. This adsorption leads to changes in the absorption spectra related to the complex formation. The apparent association constant (Kapp) was in the order of 4.34-5.58 x 10(5) M(-1) from the effect of colloidal CdS on the absorption spectra and 0.64-1.6 x 10(5) M(-1) from fluorescence quenching data. Quenching is attributable mainly to static mechanism through ground state complex formation as confirmed by lifetime measurements.

Size tunable synthesis of cysteine-capped CdS nanoparticles by γ-irradiation

Highly water soluble and biocompatible L-cysteine-capped CdS nanoparticles having narrow size distribution were synthesized for the first time by gamma-irradiation technique without using any additional stabilizer. FTIR study shows that CdS nanoparticles are capped through mercapto-group of cysteine amino acid while its free amino and carboxylate groups make it amenable to bio-conjugation. Size and luminescence of the nanoparticles can be well controlled by varying the parameters like radiation dose, pH and concentration of cysteine. The observed results suggest that pH 7 can be optimum for the synthesis of L-cysteine-capped CdS nanoparticles. CdS nanoparticles synthesized with molar ratio of Cd(2+):cysteine, 1:60 at pH 7 were found to be most luminescent. All nanoparticles formed lie in the size quantization regime and exhibit good crystallinity. Remarkable improvement in stability and luminescence was achieved on changing pH of as-prepared nanoparticles from 7 to 11.