The effect of polyelectrolyte chain flexibility on adsorption to oppositely charged colloidal particles and its parametrization by persistence length have been investigated by comparison of PDADMAC and chitosan, polycations of equal linear charge density but of respectively low and high bare persistence lengths, relatively. Their relative affinity to (i) nonionic/anionic mixed micelles, (ii) carboxyl-terminated dendrimers, and (iii) bovine serum albumin (BSA) was studied by turbidimetric titrations. Potentiometric titrations and dynamic light scattering experiments as well as molecular modeling with SPARTAN were used to characterize and model these systems. The experimental and modeling results lead to the conclusion that while chain stiffness does influence the binding of polyelectrolytes to oppositely charged colloids, the persistence length is not necessarily an appropriate measure of chain flexibility on short length scales.

The sonochemically driven synthesis of CdSe quantum dots (QDs) and their subsequent sonochemical ZnS shelling is described. By adapting the use of Cd(OAc) 2 , TOPO, and hexadecylamine to an ultrasounddriven synthesis and by applying a subsequent sonochemical ZnS shelling procedure to CdSe QD cores using Zn-ethylxanthate, highly luminescent QDs with quantum yields of 50% to 60%, narrow emission spectra (fwhm ∼25 nm), and size distributions of ∼10% were obtained. Furthermore, QD synthesis via ultrasound has several attractive features, such as a straightforward process control in the absence of any outside heat source and the ability to achieve nucleation and growth at bulk temperatures notably lower than those required for thermal techniques. The approach presented herein is accessible to laboratories with limited synthetic expertise to create CdSe/ZnS QDs.

The current study reports on the colloidal stabilities and emission properties of CdSe/ZnS quantum dot (QD) optical probes capped with a variety of thin, hydrophilic surface coatings as studied using confocal fluorescence correlation spectroscopy. These coatings are based on mercaptoethanol, mercaptopropionic acid (with and without conjugated aminoethoxyethanol), lipopolymers (DSPE-PEG2000), cysteine (Cys), and a variety of Xaa-Cys dipeptides. The study shows that several types of QDs with thin hydrophilic coatings can be designed that combine good colloidal stability and excellent emission properties (brightness). Furthermore, there is a general correlation between colloidal stability and brightness. The experiments reported herein illustrate that QDs with multiple types of thin coatings can be created for optical imaging applications in a biological environment while also maintaining a size below 10 nm.

Sonochemistry H 3000Facile Sonochemical Synthesis of Highly Luminescent ZnS-Shelled CdSe Quantum Dots. -Highly luminescent quantum dots with quantum yields of 50 to 60%, narrow emission spectra, and size distributions of about 10% are prepared by sonochemically ZnS shelling of CdSe quantum dot cores which are also sonochemically obtained starting with Cd(OAc)2, trioctyl phosphine oxide, and hexadecylamine. Quantum dot synthesis via ultrasound has several attractive features, such as straightforward process control in the absence of any outside heat sources and the ability to achieve nucleation and growth at bulk temperatures notably lower than those required for thermal techniques. The approach is accessible to laboratories with limited synthetic expertise to create CdSe/ZnS quantum dots. -(MURCIA, M. J.; SHAW, D. L.; WOODRUFF, H.; NAUMANN*, C. A.; YOUNG*, B. A.; LONG, E. C.; Chem.