Effect of surface modification with various thiol compounds on colloidal stability of gold nanoparticles

Gold nanoparticles (AuNPs) are attractive materials due to their special optical and electronic properties. However, they tend to aggregate particularly in the presence of thiol‐containing compounds. In this study, to investigate the effect of surface conjugation with thiol‐containing compounds on colloidal stability, thiol compounds with various structures as modifying agents were used. To this end, AuNPs were synthesized and stabilized by trisodium citrate in aqueous solution, and then modified with thiol‐containing compounds, namely cysteamine hydrochloride (MEA, containing primary amine groups), 2‐mercaptoethanol (BME, containing hydroxyl groups), 1‐dodecanthiol (LCA, containing long‐chain alkyl groups) and thioglycolic acid (TGA, containing carboxylic acid groups). We studied the effect of thiol ligands on solution stability of colloidal AuNPs and on the formation of aggregates originating from the modification process using UV–visible spectroscopy, dynamic light scattering, field emission scanning electron microscopy and transmission electron microscopy. Results showed that surface modification with MEA, BME and LCA led to the formation of aggregates. However, conjugation with TGA showed a concentration‐dependent behaviour: surface modification with low concentration resulted in the formation of aggregates whereas that with high concentration of TGA did not disturb the colloidal stability of AuNPs. Finally, the effect of surface modification on temperature increase of solutions originating from infrared light irradiation was studied, where the temperature increase depends on the surface‐modifying compound.     

Simultaneous Investigation of the Laser Intensity and Magnetic Field Effects on Laser-Induced Plasma Spectroscopy

Journal of Russian Laser Research - In this paper, we use laser-induced breakdown spectroscopy (LIBS) to investigate the laser-induced copper plasma with and without an external magnetic field,...     

Design and synthesis of benzodiazepine-1,2,3-triazole hybrid derivatives as selective butyrylcholinesterase inhibitors

Molecular Diversity - A new series of compounds based on benzodiazepine-1,2,3-triazole were synthesized and evaluated as cholinesterase inhibitors by Ellman’s method. The compounds proved to...     

n-Bit Quantum Secret Sharing Protocol Using Quantum Secure Direct Communication

International Journal of Theoretical Physics - The proposed quantum secret sharing protocol in this article conveys n bit secret messages from the sender to the n receivers making use of a secure...     

DFT study of adenine–cytosine mismatch in quaternary systems involving DNA bases

Structural Chemistry - In the present work, the adenine–cytosine mismatch is theoretically investigated in quaternary systems involving DNA bases. The calculations, in gas phase, are...     

Carbon–carbon coupling reactions catalyzed by supported Pd porphyrins

The tetrakis(4‐N‐methylpyridinium)porphyrinatopalladium(II) iodide, [Pd(TMPyP)]I₄, supported on Dowex 50WX8 and Amberlite IR‐120 ion‐exchange resins, was used as heterogeneous, recyclable and active catalyst for the Suzuki–Miyaura and Heck cross‐coupling reactions. These catalysts were applied to coupling of various aryl halides with phenylboronic acid and styrene in Suzuki and Heck reactions, respectively, and the corresponding products were obtained in excellent yields and short reaction times. The catalysts could be recovered easily by simple filtration and reused several times without significant loss of their catalytic activity. The catalysts were characterized by diffuse‐reflectance UV–visible spectroscopy and scanning electron microscopy, and their stability was confirmed by TGA. Copyright © 2014 John Wiley & Sons, Ltd.