Dalton Transactions Blog

Gold nanoparticles (Au-NPs) are attractive for applications in important technological fields as components of biosensors, novel catalysts and new optical, magnetic or electrical devices. Traditional techniques for their preparation include thermal decomposition of organometallic precursors, chemical reduction of Au(I) ions, and electrochemical and photochemical processes. Methods based on reduction by sodium borohydride or citrate ions have been used successfully as the reducing agent acts also as a stabilizer and prevents further aggregation.

As an alternative, Heinrich Lang, from Chemnitz University of Technology, and coworkers have developed a family of gold(I) carboxylate complexes which can be used as precursors for the preparation of Au-NPs in a single step. The ligand works as the reducing and stabilizing part, simultaneously, in one molecule. After thermally induced decomposition of the complexes, Au-NPs are obtained with sizes in the range from 3.3 to 6.5 nm, and almost homogenous size distribution. The ethylene glycol-functionalized carboxylates were obtained from easy chemical reactions using available ethylene gycol or directly from commercial suppliers, and the complexes obtained by a two step procedure.  The authors report than larger chain lengths increased stability and slowed particle growth.

To find out more about it, read the full paper in Dalton Transactions.

Gold nanoparticles generated by thermolysis of “all-in-one” gold(I) carboxylate complexes
André Tuchscherer, Dieter Schaarshmidt, Steffen Schulze, Michael Hietschold, Heinrich Lang,
Dalton Transactions, 2012, Advance Article
DOI: 10.1039/c2dt11748g

To catch a bacterial infection after a visit to a hospital for a health checkup is not a funny way to become sick. Even worse is when the infection came from a device which was supposed to help you to get better, not sicker, such as a medical device. Intra-hospital infections are difficult to avoid as some viruses or bacterias deposit on any surface available, which may become in contact with a healthy person, with potential health consequences.  Numerous approaches have been looked at in order to create materials with anti-bacterial capabilities. In this direction, silver and copper nanoparticles (AgNP and CuNP) are attractive as they may be able to avoid propagation of several microorganisms, including E. coli and S. aureus. Several methods have been tried to successfully immobilize the nanoparticles to a surface.

Giacomo Dacarro and coworkers at the Università degli Studi di Pavia at Italy, have devised a new way to chemically modify Si-OH terminated surfaces (glass, quartz, SiO₂) by using a novel silane-derivatized polyethylenimine (PEI) and testing its ability to coordinate Ag⁺ and Cu²⁺ ions, and silver nanoparticles. The functionalized glasses are very effective in fighting against E. coli and S. aureus propagation, and may be an novel platform for use in designing smart, hybrid multifunctional materials.

Read more about his paper published in Dalton Transactions.

Monolayers of polyethilenimine on flat glass: a versatile platform for cations coordination and nanoparticles grafting in the preparation of antibacterial surfaces
Giacomo Dacarro, Lucia Cucca, Pietro Grisoli, Piersandro Pallavicini, Maddalena Patrini and Angelo Taglietti
Dalton Trans., Advance Article, 2012.
DOI: 10.1039/c1dt11373a 

Noble metals are highly regarded as unique catalysts for use in several reactions, many of them of interest for the pharmaceutical industry. However, their cost may be a reason why not to be considered in several applications.  When used in the form of nanoparticles, an increase of their activity is expected as a result of their large specific surface area, even when small amounts are used, which can save money and time. In the search for more efficient ways to form C-N bonds, a variety of homogenous catalysts such as Cu, Pd and Rh have been investigated in order to tune them and improve their ability to promote cross-coupling reactions among aryl halides and amines. Specifically, copper mediated Ullmann condensation is attractive as it is cheaper than Pd or Rh.

Zhenhui Kang and his group at the Institute of Functional Nano and Soft Materials and the Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices at Soochow University have developed a new catalyst based on copper nanoparticles inmovilized on silicon nanowires (CuNPs@SiNWs). This catalyst is able to enhance the coupling reaction at 110 °C among benzene halides and aniline in good yields, without the use of any ligand or additive. Even deactivated aryl bromides and inert chlorobenzene were reactive under the action of this novel catalysts. The authors suggest that the use of SiNWs as an alternative substrate support may be of interest of other researchers in the quest of superior heterogeneous catalysts.  

For further information, read the work by Zhenhui Kang and coworkers published in Dalton Transactions.

Copper nanoparticles modified silicon nanowires with enhanced cross-coupling catalytic ability
Keming Pan, Hai Ming, Hang Yu, Hui Huang, Yang Liu, Zhenhui Kang
Dalton Trans., Advance Article, 2012.
DOI: 10.1039/c2dt12182d