Protein-activated transformation of silver nanoparticles into blue and red-emitting nanoclusters.

Proteins are very effective capping agents to synthesize biocompatible metal nanomaterials . Reduction of metal salts in the presence of a protein generates very different types of nanomaterials (nanoparticles or nanoclusters) at different pH. Can a simple pH jump trigger a transformation between the nanomaterials? This has been realized through the conversion of silver nanoparticles (AgNPs) into highly fluorescent silver nanoclusters (AgNCs) a pH-induced activation with bovine serum albumin (BSA) capping.

Anomalous Spectral Modulation of 4-Aminophthalimide inside Acetonitrile/AOT/ n-Heptane Microemulsion: New Insights on Reverse Micelle to Bicontinuous Microemulsion Transition.

The behavior of acetonitrile/sodium 1,4-bis(2-ethylhexyl)sulfosuccinate (AOT)/ n-heptane microemulsion, whether it remains as reverse micelle (RM) or bicontinuous microemulsion (BMC), has been controversial and even termed as a "problem system". Herein, we investigate the microemulsion using spectral and dynamical responses of a hydrophilic solvatochromic fluorophore 4-aminophthalimide (4-AP) at different w values (=[acetonitrile]/[AOT]). Interestingly, we found that emission parameters of 4-AP within the microemulsion vary differently at low and high w regimes.

A New Phase Transfer Strategy to Convert Protein-Capped Nanomaterials into Uniform Fluorescent Nanoclusters in Reverse Micellar Phase.

A new phase transfer strategy to convert aqueous phase protein-protected nanomaterials into fluorescent nanoclusters in the reverse micellar environment is introduced using bovine serum albumin (BSA)-protected silver nanoclusters (AgNCs) and nanoparticles (AgNPs) as an example. The basic pH employed in the fabrication of protein-protected nanoclusters induces the the protein capping to be negatively charged and facilitates the transfer process of the nanomaterials from aqueous phase to a cationic gemini surfactant (16-2-16)/hexane/hexanol/water reverse micelle (RM) phase. The original fluorescence characteristics of the seed nanocluster is retained after the transfer process.

Coupling of Molecular Transition with the Surface Plasmon Resonance of Silver Nanoparticles inside the Restricted Environment of Reverse Micelles.

Interaction of molecular transitions of two fluorophores-fluorescein (FL) and safranin O (SAF)-with the surface plasmon resonance (SPR) of silver nanoparticles (AgNPs) inside a water/sodium dioctylsulfosuccinate (AOT)/-heptane reverse micelle (RM) has been studied using ultraviolet-visible and fluorescence spectroscopies. Here, we exploit the natural capacity of a RM to act simultaneously as a template for nanoparticle formation and host the fluorophores. The fluorophores and reducing agent were loaded together into the water pool; thereafter, silver salt was added, and subsequently, spectral modification and size evolution were monitored by steady-state and time-resolved optical spectroscopy.