Butterfly wings as hard templates for nano metals

Templating is an age-old technique since the first human settlers shaped clay in wooden boxes. Several thousand years later, mesoscale architects used porous silica as hard templates (just like wooden boxes) to give form to carbon and other important matter. Now some brilliant scientists have copied one of the most delicate beings of the biosphere, the butterflies.

Dip coating CdSe nanorod tips with Gold

Sheldon et al. (from Alivisatos group at UC Berkeley) reported 100,000 fold increase in the conductance of the CdSe nanorods by dipping the ends into gold. The procedure they followed was very simple:

a toluene solution containing gold trichloride (AuCl3, 12 mg, 0.04 mmol), didodecyldimethylammonium bromide (DDAB, 40 mg, 0.08 mmol), and dodecylamine (DDA, 70 mg, 0.37 mmol) was sonicated for 5 min and then added dropwise to a suspension of nanorods stirring under N2. The product was precipitated with methanol
and separated by centrifugation.

Gold nanoparticles for lung cancer detection

Nature Nano published an article yesterday by Peng et al. (from Hossam Haick's group at Technion) claiming lung cancer detection by a breathe analyzer based on gold nanoparticles and the resistivity change upon contact with the patient's breathe.

Thin film of thiols with a monolayer of gold particles are wrapped into compartments that are called chemiresistors. The difference in the resistance to the applied current gives away if you have some of the characteristic volatile organic compounds (VOCs).

8 nm Au Ag nano alloys for CO oxidation

Dr. Sun did it again!
There wasn't an easy way to make gold and silver nano scale alloys (especially at the sizes of 8-9 nm) until Dr. Shouheng Sun and Dr. Chao Wang's work appeared in chemistry of materials just yesterday. The method shines with its simplicty: one pot, mix silver nitrate (AgNO3) with oleylamine, heat it to 100 oC, inject HAuCl4, heat more at 120 oC for 30 more minutes. How simpler can it get? Results are stunning (see the figure); you can also tune the composition to your taste. The only issue is they couldn't prove that these alloys survive CO oxidation without any sintering. I think this is the reason they published a communication. Let's wait for the fully loaded beauty.

Growth of PS beads on gold nanocrystals

Ohnuma et al. (Xia group at Washington U. St. Louis) presents a beautiful way of dressing up gold nanocrystals with polystyrene (PS) polymer. They start the polymerization and then introduce the gold (50 nm) nanocrystals at a magic time, 2 minutes after the initiation. 30 minutes had 50 % success for gold embedding and 0 minutes had multiple gold cores in PS particles (in all cases PS size was around 300 nm with somewhat round shape). I wonder if plasmonic resonance played a role in the growth of the PS. As they promised to publish a mechanistic paper, we'll have to wait.

Robust Gold Nanoparticles

I'd never think there would be new ways to make gold nanoparticles. Especially more robust. We know well that gold likes to get involved with other stuff in a solution. But Dong et al. (from Matyjaszewski group at Carnegie Mellon) showed that they can form the nanoparticles with a thick robust shell right out of the pot. They even heated the solutions up to 110 oC! And yet their nano gold didn't lose their surface plasmon resonance (just compare the left -the usual- and right -theirs- in the figure posted here). Pretty amazing.