Copolymer-induced stabilizing effect of highly swollen hexagonal mesophases

We show quantitatively that tiny amounts of copolymer that decorate a oil/water interfaces can greatly enhance the stability of swollen surfactant hexagonal phases, comprising oil tubes regularly arranged in a water matrix. Such soft composite materials, whose both radius of the tubes and water channel between the tubes can be controlled independently over large ranges, offer a potential interest for the synthesis of mesoporous materials

Introduction to celebrating Latin American talent in chemistry

In celebration of the excellence and breadth of Latin American research achievements across the chemical sciences, we are delighted to present an introduction to the themed collection, Celebrating Latin American talent in chemistry. [Image: see text

Hybrid titania microspheres of novel superstructures templated by block copolymers

Chemistry of Materials23112745-2752CMAT

Structure, Dynamics, and Phase Behavior of Water in TiO2 Nanopores

Mesoporous titania is a highly studied material due to its energy and environment-related applications, which depend on its tailored surface and electronic properties. Understanding the behavior of water in titania pores is a central issue for practical purposes in photocatalysis, solar cells, bone implants, or optical sensors. In particular, the mechanisms of capillary condensation of water in titania mesopores and the organization and mobility of water as a function of pore filling fraction are not yet known. In this work, molecular dynamics simulations of water confined in TiO2-rutile pores of diameters 1.3, 2.8, and 5.1 nm were carried out at various water contents. Water density and diffusion coefficients were obtained as a function of the distance from the surface. The proximity to the interface affects density and diffusivity within a distance of around 10 Å from the walls, beyond which all properties tend to converge. The densities of the confined liquid in the 2.8 and the 5.1 nm pores decrease, respectively, 7% and 4% with respect to bulk water. This decrease causes the water translational mobility in the center of the 2.8 nm pore to be appreciably larger than in bulk. Capillary condensation takes place in equilibrium for a filling of 71% in the 2.8 nm pore and in conditions of high supersaturation in the 5.1 nm pore, at a filling of 65%. In the former case, the surface density increases uniformly with filling until condensation, whereas in the larger nanopore, a cluster of water molecules develops on a localized spot on the surface for fillings just below the transition. No phase transition is detected in the smaller pore. For all the systems studied, the first monolayer of water is strongly immobilized on the interface, thus reducing the accessible or effective diameter of the pore by around 0.6 nm. As a consequence, the behavior of water in these pores turns out to be comparable to its behavior in less hydrophilic pores of smaller size.Fil: Gonzalez Solveyra, Estefania. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Quimica Fisica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: de la Llave, Ezequiel Pablo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Quimica Fisica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Molinero, Valeria. University of Utah; Estados UnidosFil: Soler Illia, Galo Juan de Avila Arturo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Quimica Fisica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Comision Nacional de Energia Atomica. Centro Atomico Constituyentes; ArgentinaFil: Scherlis Perel, Damian Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de Los Materiales, Medioambiente y Energía; Argentina. Universidad de Buenos Aires; Argentin

Block Copolymer Directed Ordered Mesostructured TiNb2O7 Multimetallic Oxide Constructed of Nanocrystals as High Power Li-Ion Battery Anodes

In order to achieve high-power and -energy anodes operating above 1.0 V (vs Li/Li+), titanium-based materials have been investigated for a long time. However, theoretically low lithium charge capacities of titanium-anodes have required new types of high-capacity anode materials. As a candidate, TiNb2O7 has attracted much attention due to the high theoretical capacity of 387.6 mA h g-1. However, the high formation temperature of the TiNb2O7 phase resulted in large-sized TiNb2O7 crystals, thus resulting in poor rate capability. Herein, ordered mesoporous TiNb2O7 (denoted as m-TNO) was synthesized by block copolymer assisted self-assembly, and the resulting binary metal oxide was applied as an anode in a lithium ion battery. The nanocrystals (???15 nm) developed inside the confined pore walls and large pores (???40 nm) of m-TNO resulted in a short diffusion length for lithium ions/electrons and fast penetration of electrolyte. As a stable anode, the m-TNO electrode exhibited a high capacity of 289 mA h g-1 (at 0.1 C) and an excellent rate performance of 162 mA h g-1 at 20 C and 116 mA h g-1 at 50 C (= 19.35 A g-1) within a potential range of 1.0-3.0 V (vs Li/Li+), which clearly surpasses other Ti-and Nb-based anode materials (TiO2, Li4Ti5O12, Nb 2O5, etc.) and previously reported TiNb2O 7 materials. The m-TNO and carbon coated m-TNO electrodes also demonstrated stable cycle performances of 48 and 81% retention during 2,000 cycles at 10 C rate, respectively.close6