ABSTRACT
The mechanism of the two-phase Brust-Schiffrin synthesis of alkane thiol protected metal nanoparticles is known to be highly sensitive to the precursor species and reactant conditions. In this work X-ray absorption spectroscopy is used in conjunction with liquid/liquid electrochemistry to highlight the significance of Br- in the reaction mechanism. The species [AuBr4]- is shown to be a preferable precursor in the Brust-Schiffrin method as it is more resistant to the formation of Au(i) thiolate species than [AuCl4]-. Previous literature has demonstrated that avoidance of the Au(i) thiolate is critical to achieving a good yield of nanoparticles, as [Au(i)X2]- species are more readily reduced by NaBH4. We propose that the observed behavior of [AuBr4]- species described herein explains the discrepancies in reported behavior present in the literature to date. This new mechanistic understanding should enable nanoparticle synthesis with a higher yield and reduce particle size polydispersity.
ABSTRACT
Digestive tract cancers are infrequent during pregnancy. Prognosis is usually dismal both because diagnosis is delayed as a result of symptoms being ascribed to the pregnancy and because saving both the mother and fetus is difficult. A review of the relevant literature, focused on colorectal and gastric cancers which are the most common forms, emphasizes the need for early diagnosis and for adjusting treatment to gestational age at diagnosis.
