02206nas a2200157   4500008004100000022001400041245014700055210006900202260000900271300001600280490000700296520156900303100002601872700002301898856012701921       2021                        eng d  a2040-336400aImplication of adsorption preferences of ions and surfactants on the shape control of gold nanoparticles: a microscopic, atomistic perspective0 aImplication of adsorption preferences of ions and surfactants on  cDEC   a19549-195600 v133 aShape modulation of nanoparticles is crucial for their tailored applications; however, it depends on surfactants, ions, reactants, and other additives present in the growth solution. Here we dissect the role of surfactants, their counterions (halide ions), silver ions, and gold reactant in gold nanoparticle anisotropic growth using polarizable surfaces and nanoseed molecular dynamics simulation models. Our planar surface models predict a 14%-16% increment in cetyltrimethylammonium bromide (CTAB) coverage on Au(111) and Au(100) due to the surface polarization effect. The CTAB micelle adsorbs compactly similar to that observed on non-polarizable surfaces. The cetyltrimethylammonium chloride (CTAC) micelle remains in solution leaving the polarizable gold surfaces unprotected, similar to that observed with the non-polarizable surfaces, which favors isotropic growth. The cetyltrimethylammonium iodide (CTAI) micelle adsorbs with higher surface densities than CTAB on all the surfaces. The surface polarizable penta-twinned nanoseed model predicts the total surface coverage of the cetyltrimethylammonium cation (CTA(+)), Br- and Ag+ to be around two times higher on the side as compared to the tip of the nanoseed, leading to a 2.6 times higher initial rate of adsorption of AuCl2- on the tip than on the side. Predicted CTA(+) surface densities on the tip and the side of the nanoseed are consistent with experimental results. Our simulations explain the growth mechanism of anisotropic nanoparticles and the microscopic origin of their controlled shapes.1 aMeena, Santosh, Kumar1 aMeena, Chandrakala  uhttp://library.ncl.res.in/content/implication-adsorption-preferences-ions-and-surfactants-shape-control-gold-nanoparticles01967nas a2200229   4500008004100000022001400041245008700055210006900142260000800211300001600219490000700235520121400242100002601456700002201482700002101504700002101525700002101546700002101567700002301588700001801611856010801629       2021                        eng d  a2040-336400aOn the origin of controlled anisotropic growth of monodisperse gold nanobipyramids0 aorigin of controlled anisotropic growth of monodisperse gold nan  cSEP  a15292-153000 v133 aWe elucidate the crucial role of the cetyl trimethylammonium bromide (CTAB) surfactant in the anisotropic growth mechanism of gold nano-bipyramids, nano-objects with remarkable optical properties and high tunability. Atomistic molecular dynamics simulations predict different surface coverages of the CTAB (positively charged) heads and their (bromide) counterions as function of the gold exposed surfaces. High concentration of CTAB surfactant promotes formation of gold nanograins in solution that work as precursors for the smooth anisotropic growth of more elongated nano-bipyramidal objects. Nanobipyramids feature higher index facets with respect to nanorods, allowing higher CTAB coverages that stabilize their formation and leading to narrower inter-micelles channels that smooth down their anisotropic growth. Absorption spectroscopy and scanning electron microscopy confirmed the formation of nanograins and demonstrated the importance of surfactant concentration on driving the growth towards nano-bipyramids rather than nanorods. The outcome explains the formation of the monodisperse bipyramidal nano-objects, the origin of their controlled shapes and sizes along with their remarkable stability.1 aMeena, Santosh, Kumar1 aLerouge, Frederic1 aBaldeck, Patrice1 aAndraud, Chantal1 aGaravelli, Marco1 aParola, Stephane1 aSulpizi, Marialore1 aRivalta, Ivan  uhttp://library.ncl.res.in/content/origin-controlled-anisotropic-growth-monodisperse-gold-nanobipyramids