A General Assembly

A General Assembly

Author: Angewandte Chemie International Edition

Researchers at Northwestern University, USA, have described nanoparticle crystals of different internal architectures and stabilized with chemically cleavable cross-links effectively “amplify” the presence of cross-link-specific analytes.

Bartosz Grzybowski and co-workers employed Au and Ag nanoparticles (NPs) with self-assembled monolayers of suitable dithiols (either positively charged N,N,N-trimethyl(11-mercaptoundecyl)ammonium chloride or negatively charged, deprotonated mercaptoundecanoic acid) to detect and amplify the presence of chemical and enzymatic analytes. The cross-linked crystals are insoluble in water and when an analyte (an anion, a small molecule, or an enzyme) is present, it cuts the cross-linkers so that each crystal liberates millions of individual, highly colored NPs. Effectively, once a small hole is “pinched” in the crystal’s cross-linked “skin” NPs spill from the crystal’s interior into solution (see figure). This mode of sensing has general potential for different cross-link/analyte combinations.


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