Photochemical and thermal spiropyran (SP)-merocyanine (MC) interconversion: a dichotomy in dependence on viscosity.

The current study extends our work with spiropyran-merocyanines (SP-MC) as molecular photoswitches by delving into the effects of viscosity. This has led to the interesting finding of a dichotomy in viscosity dependence. Solutions of SP [6'-nitro-1,3,3-trimethylspiro(indolino-2,2'-benzopyran)] in a wide range of ethylene glycol-methanol (EG-MeOH) media (3.

Elucidating the mechanisms of acidochromic spiropyran-merocyanine interconversion.

The thermal and photochemical processes associated with the acid-induced conversions of 6-nitroBIPS, SP-1, to form the protonated merocyanine (MC-OH+) were investigated via UV/vis spectrophotometric studies in acetone. It was found that the mechanism of trifluoroacetic acid (TFA)-induced ring-opening of the SP and the rate of MC-OH+ formation follows a general acid catalysis mechanism. In accord with this mechanism, the thermal growth of the acid-induced ring-opened form (MC-OH+) was retarded as the concentration of TFA in the medium was increased.

Formation, characterization, and chemistry of undecanoic acid-terminated silicon surfaces: patterning and immobilization of DNA.

This paper describes a simple strategy for DNA immobilization on chemically modified and patterned silicon surfaces. The photochemical modification of hydrogen-terminated Si(111) with undecylenic acid leads to the formation of an organic monolayer covalently attached to the surface through Si-C bonds without detectable reaction of the carboxylic acid group, providing indirect support of a free radical mechanism. Chemical activation of the acid function was achieved by a simple chemical route using N-hydroxysuccinimide (NHS) in the presence of N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide hydrochloride.